JP2024074175A - Ground load estimation device, suspension device, and ground load estimating program - Google Patents

Abstract

To provide a ground load estimation device capable of accurately estimating a ground load at low cost, a ground load estimating program capable of accurately estimating the ground load at low cost, and a suspension device capable of controlling the ground load at low cost.SOLUTION: A ground load estimation device 1 includes: an unsprung vibration detection portion 2 for detecting speed and displacement in a vertical direction of an unsprung member W in a vehicle; a deflection amount detection portion 3 for detecting a deflection amount in the vertical direction of a tire in the unsprung member W; an observer 4 for outputting estimated speed and estimated displacement in the vertical direction of the unsprung member W based on a state equation of the unsprung member W of a one wheel model by receiving input of the speed and displacement of the unsprung member W and the deflection amount of the tire as an observation amount, and estimated displacement change rate and estimated displacement of a road surface R; and a grounding load computing portion 5 for computing a grounding load fw of the unsprung member W based on the estimated speed and the estimated displacement of the unsprung member W estimated by the observer 4, and the estimated displacement change rate and the estimated displacement of the road surface R.SELECTED DRAWING: Figure 2

Description

The present invention relates to a ground load estimation device, a suspension device, and a ground load estimation program.

In conventional suspension devices, for example, there are those that temporarily increase the ground load of the wheels to prevent the wheels from spinning when the vehicle accelerates suddenly. Such suspension devices are equipped with an actuator that is interposed between the body and wheels of the vehicle, and a controller that controls the actuator. When sudden acceleration of the vehicle is detected, the controller determines whether the wheels are in a state where they may spin, and if there is a possibility that the wheels may spin, the actuator is activated to temporarily increase the ground load of the wheels, thereby preventing the wheels from spinning (for example, see Patent Document 1).

Japanese Patent Application Laid-Open No. 10-297239

As mentioned above, conventional suspension systems increase the wheel ground load when there is a possibility of the wheels spinning, but because they do not detect the wheel ground load itself and are therefore unable to grasp the ground load, they are unable to control the ground load accurately.

In theory, the ground contact load can be calculated using the following equation (1) by solving the equation of motion for a one-wheel model including the body and wheel shown in Figure 5. In equation (1), Mb represents the mass of the vehicle body 101 supported by one wheel (unsprung member) 100 of the vehicle, xb represents the displacement of the vehicle body 101, Mt represents the mass of the wheel 100, xt represents the displacement of the wheel 100, xr represents the displacement of the road surface on which the wheel 100 runs, fb represents the external force acting on the vehicle body 101, Cs represents the base damping coefficient of the shock absorber 102 with adjustable damping force interposed between the vehicle body 101 and the wheel 100, Ks represents the spring constant of the suspension spring 103 interposed between the vehicle body 101 and the wheel 100, Ct represents the viscosity coefficient of the tire at the wheel 100, Kt represents the spring constant of the tire, and u represents a control command indicating the damping force adjustment amount to be loaded on the base damping force of the shock absorber 102. In the formulas in this book, a variable with one dot above it indicates the derivative of the variable, and a variable with two dots above it indicates the second derivative of the variable.

To obtain the ground load from equation (1), information on the acceleration of the vehicle body 101 and the acceleration of the wheels 100, or the acceleration of the wheels 100, the damping force generated by the shock absorber 102, and the spring force generated by the suspension spring 103 is required. To obtain the acceleration of the vehicle body 101 and the acceleration of the wheels 100, it is necessary to attach acceleration sensors to the suspension arms supporting the vehicle body 101 and the wheels 100. Also, to obtain the damping force generated by the shock absorber 102 and the spring force of the suspension spring 103, information on the expansion and contraction speed of the shock absorber 102 is required, so a stroke sensor must be installed on the shock absorber 102. In this way, at least two or more sensors are required to obtain the ground load, and since the external force acting on the vehicle body 101 cannot be detected by installing a sensor, the ground load cannot be obtained accurately.

The present invention aims to provide a ground load estimation device that can accurately estimate ground load at low cost, a ground load estimation program that can accurately estimate ground load at low cost, and a suspension device that can control ground load at low cost.

In order to achieve the above object, the ground load estimation device in the problem-solving means of the present invention includes an unsprung vibration detection unit that detects the vertical speed and displacement of the unsprung member in the vehicle, a deflection amount detection unit that detects the vertical deflection amount of the tire in the unsprung member, an observer that receives the speed and displacement of the unsprung member and the deflection amount of the tire as observation amounts and outputs the estimated vertical speed and estimated displacement of the unsprung member and the estimated displacement change rate and estimated displacement of the road surface based on the state equation of the unsprung member of the one-wheel model, and a ground load calculation unit that calculates the ground load of the unsprung member based on the estimated speed and estimated displacement of the unsprung member estimated by the observer and the estimated displacement change rate and estimated displacement of the road surface.

The ground load estimation program of the present invention causes a computer to execute processing including an unsprung vibration detection step for detecting the vertical speed and displacement of the unsprung member in the vehicle, a deflection amount detection step for detecting the vertical deflection amount of the tire in the unsprung member, an estimate calculation step for inputting the speed and displacement of the unsprung member and the deflection amount as observed amounts to an observer that outputs the estimated vertical speed and estimated displacement of the unsprung member and the estimated displacement change rate and estimated displacement of the road surface based on the state equation of the unsprung member of the one-wheel model, and calculating the estimated speed and estimated displacement of the unsprung member and the estimated displacement change rate and estimated displacement of the road surface, and a ground load calculation step for calculating the ground load of the unsprung member based on the estimated speed and the estimated displacement and the estimated displacement change rate and estimated displacement of the road surface.

In the ground load estimation device and ground load estimation program configured in this manner, the speed and displacement of the unsprung member and the amount of tire deflection are input to an observer to determine the road surface displacement change rate and road surface displacement required to determine the ground load, so the only sensor required to determine the ground load is an acceleration sensor that detects the acceleration of the unsprung member, which is required to detect the speed and displacement of the unsprung member. Furthermore, the ground load estimation device and ground load estimation program can accurately determine the ground load without requiring information on the external forces acting on the sprung member.

The observer in the ground load estimation device may be an observer of an extended system that regards all forces received from the sprung member side of the vehicle as disturbances. With a ground load estimation device configured in this way, the spring force of the suspension spring and the damping force of the damping force variable damper received from the sprung member side are included in the disturbances such as aerodynamic forces acting on the sprung member, eliminating the need to input control input to the observer, and thus eliminating response delays due to control input, making it possible to calculate the ground load with even greater accuracy.

Furthermore, in the ground load estimation device, the ground load calculation unit may determine the ground load based on the tire spring constant and viscous resistance constant, and may include a setting unit that sets the spring constant and viscous resistance coefficient. With a ground load estimation device configured in this manner, the spring constant and viscous resistance coefficient can be set to optimal values for calculating the ground load according to the tire used in the unsprung member of the vehicle, making it possible to determine the ground load with even greater accuracy.

The suspension device is provided with a suppression force generating device that is interposed between the sprung and unsprung members of the vehicle and is capable of exerting a suppression force that suppresses relative movement between the sprung and unsprung members in the vertical direction, and that is capable of changing the suppression force, a controller that controls the suppression force generating device, and a ground load calculation device, and the controller may control the suppression force exerted by the suppression force generating device based on the ground load determined by the ground load estimation device. The suspension device configured in this manner is provided with a ground load estimation device that can estimate the ground load at low cost, and therefore the ground load can be controlled at low cost.

As described above, the ground load estimation device and ground load estimation program of the present invention can estimate the ground load accurately at low cost, and the suspension device of the present invention can control the ground load at low cost.

1 is a diagram showing a suspension device that utilizes a ground load estimation device according to an embodiment; FIG. 1 is a diagram showing a configuration of a ground contact load estimation device according to an embodiment. FIG. 13 is a diagram showing an unsprung member of a vehicle in a one-wheel model. 4 is a flowchart showing an example of a processing procedure of the ground contact load estimation device according to the embodiment; FIG. 13 is a diagram showing a sprung member and an unsprung member in a one-wheel model.

The present invention will be described below based on the embodiment shown in the drawings. As shown in FIG. 1, the ground load estimation device 1 in this embodiment estimates the ground load fw input to a controller C in a suspension device 10 interposed between a sprung member B, such as a vehicle body that is elastically supported by a suspension spring S in a vehicle V, and an unsprung member W that includes wheels. The ground load fw is a vertical force acting from the road surface R on the unsprung member W in the vehicle V, and the controller C uses the ground load fw to determine the suppression force to be generated in the variable damping force damper D in the suspension device 10.

Below, the ground load estimation device 1 and the suspension device 10 that utilizes the ground load estimation device 1 will be described in detail. First, the suspension device 10 is provided with a variable damping force damper D as a suppression force generating device that is interposed between the sprung member B and the unsprung member W of the vehicle V and is capable of exerting a suppression force that suppresses the relative movement between the sprung member B and the unsprung member W in the vertical direction and is capable of changing the suppression force, a controller C that controls the variable damping force damper D, and the ground load estimation device 1. The vehicle V is provided with a suspension spring S that is interposed between the sprung member B and the unsprung member W in parallel with the variable damping force damper D and elastically supports the sprung member B.

Although not shown in detail, the variable damping force damper D comprises a cylindrical outer shell, a piston movably inserted into the outer shell, and a piston rod movably inserted into the outer shell and connected to the piston in the axial direction. It also generates a damping force as a suppressing force that suppresses movement of the piston rod when the piston rod moves axially relative to the outer shell, and is equipped with a damping force adjustment valve that adjusts the damping force in response to a command from a controller C. The damping force adjustment valve may be, for example, a valve whose valve opening pressure and flow path area can be changed by supplying an electric current.

When the liquid filled in the outer shell of the damping force variable damper D is an electrorheological fluid or a magnetorheological fluid, the damping force variable damper D may adjust the damping force by using a device that applies an electric field or a magnetic field to the liquid to change the viscosity of the liquid instead of a damping force adjustment valve. Furthermore, the suppression force generating device may be a hydraulic actuator or an electric actuator other than the damping force variable damper D as long as it is capable of exerting a suppression force that suppresses the relative movement in the vertical direction between the sprung member B and the unsprung member W, and is not limited to a telescopic damper or actuator, but may also be a rotary damper or actuator. The suspension spring S is interposed in parallel with the damping force variable damper D between the sprung member B and the unsprung member W, and elastically supports the sprung member B.

In the suspension device 10, only one variable damper D is shown in FIG. 1, but if the vehicle V is a four-wheeled vehicle, four variable dampers D are provided between each of the four wheels and the vehicle body. A controller C does not need to be provided for each variable damper D, and one controller C may control multiple variable dampers D. Also, the controller C may be paired with a variable damper D to control one variable damper D. In FIG. 1, the spring depicted between the unsprung member W and the road surface R indicates a spring element of a tire (not shown) in the unsprung member W. In addition, the vehicle V to which the ground load estimation device 1 and the suspension device 10 are applied is not limited to a four-wheeled vehicle, and may be, for example, a two-wheeled vehicle or a three-wheeled vehicle.

The controller C includes a control unit 11 that receives the ground load fw estimated by the ground load estimation device 1 and generates a command indicating the target damping force to be generated by the damping force variable damper D, and a drive circuit 12 that receives a command from the control unit 11 and supplies current to the damping force adjustment valve. The control unit 11 generates an unsprung control command to prevent the ground load fw from becoming equal to or less than a predetermined load, for example, based on the ground load fw. The control unit 11 also generates a sprung control command that indicates the suppression force to be generated by the damping force variable damper D to suppress the vertical vibration of the sprung member B from the vertical acceleration of the sprung member B detected by the acceleration sensor 13 installed on the vehicle V. The control unit 11 then adds the unsprung control command and the sprung control command to obtain the target damping force, generates a current command that indicates the current to be supplied to the damping force adjustment valve so that the damping force variable damper D generates a damping force according to the obtained target damping force, and outputs the current command to the drive circuit 12. In this embodiment, the ground load estimation device 1, which will be described later, is equipped with an acceleration sensor 21 as shown in FIG. 2 and is unitized with the drive circuit 12 in the controller C, and is attached to the outer shell of the damping force variable damper D (not shown) as a single unit together with the drive circuit 12. The damping force variable damper D is interposed between the sprung member B and the unsprung member W with the outer shell connected to the unsprung member W. Since the ground load estimation device 1 is attached to the outer shell connected to the unsprung member W of the damping force variable damper D in this way, the acceleration sensor 21 can detect the acceleration of the unsprung member W in the vertical direction. Since the ground load estimation device 1 is equipped with the acceleration sensor 21 in this way, the control unit 11 may obtain information on the acceleration of the unsprung member W from the acceleration sensor 21 and use the acceleration of the unsprung member W in addition to the acceleration of the sprung member B to determine the sprung control command.

The drive circuit 12 feeds back the current flowing through the damping force adjustment valve, and supplies a current to the damping force adjustment valve according to the current command input from the control unit 11. The configuration of the controller C can be arbitrarily modified in design, and the processing of the control unit 11 described above is only one example, and can be arbitrarily modified in design as long as it generates a command that indicates the target damping force using the ground load fw.

As shown in FIG. 2, the ground load estimation device 1 includes an unsprung vibration detection unit 2 that detects the vertical speed and displacement of the unsprung member W of the vehicle V, a deflection amount detection unit 3 that detects the vertical deflection amount of the tire of the unsprung member W, an observer 4 that outputs the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R, and a ground load calculation unit 5 that calculates the ground load fw of the unsprung member W based on the estimated vertical speed and estimated displacement of the unsprung member W estimated by the observer 4 and the estimated displacement change rate and estimated displacement of the road surface R.

The unsprung vibration detection unit 2 includes an acceleration sensor 21 that detects the vertical acceleration of the unsprung member W, an integrator 22 that integrates the vertical acceleration of the unsprung member W detected by the acceleration sensor 21 to output the vertical velocity of the unsprung member W, and an integrator 23 that integrates the vertical velocity of the unsprung member W output by the integrator 22 to output the vertical displacement of the unsprung member W. Note that the integrators 22 and 23 may each be a pseudo-integral filter formed of a high-pass filter, or may be ones that perform an arithmetic operation to sequentially add up the accelerations detected by the acceleration sensor 21 to find the integral value.

The deflection amount detection unit 3 determines the amount of deflection of the tire at the unsprung member W based on the rotation speed of the wheel at the unsprung member W and the traveling speed of the vehicle V. Specifically, the deflection amount detection unit 3 obtains information on the rotation speed of the unsprung member W and the traveling speed of the vehicle V at a predetermined period from an ECU (Electronic Control Unit) (not shown) in the vehicle V via a CAN (Controller Area Network) bus, and determines the amount of deflection of the tire. Since the update period in which the information on the rotation speed of the unsprung member W and the traveling speed of the vehicle V obtained from the ECU is updated is longer than the calculation period of the ground load estimation device 1, the deflection amount detection unit 3 estimates the rotation speed of the unsprung member W and the traveling speed of the vehicle V at the current time by linearly interpolating the rotation speed and traveling speed up to that point in time from the time when the rotation speed and traveling speed are obtained to the time when the rotation speed and traveling speed are next updated. More specifically, if the update period is N times the calculation period, the value obtained by subtracting the rotational speed (traveling speed) from the rotational speed (traveling speed) obtained the previous time from the rotational speed (traveling speed) obtained the previous time is divided by N, and the value obtained is added to the previous rotational speed (traveling speed) for each calculation period to obtain the rotational speed (traveling speed) used when performing the calculation to obtain the tire deflection amount in the deflection amount detection unit 3. If the rotational speed obtained in this way is ω, the traveling speed is V, the reference radius of the wheel which is the unsprung member W is R, the rate of change of the tire deflection amount is dXtr, and the tire deflection amount is Xtr, then Xtr(k) = Xtr(k-1) + dXtr(k) is calculated. Here, dXtr(k) = -R{ω(k) - ω(k-1)}/V(k). Note that k indicates time.

In addition, the deflection amount detection unit 3 processes the deflection amount Xtr(k) calculated using the above-mentioned formula with a high-pass filter to remove low-frequency components contained in the deflection amount, and then removes offsets and drifts contained in the deflection amount Xtr(k) calculated in each calculation cycle to obtain the deflection amount Xtr.

When the observer 4 receives the vertical speed and displacement of the unsprung member W detected by the unsprung vibration detection unit 2 and the deflection amount detected by the deflection amount detection unit 3 as observed quantities, it outputs the estimated vertical speed and estimated displacement of the unsprung member W, and the estimated displacement change rate and estimated displacement of the road surface R based on the state equation and output equation of the unsprung member W of the one-wheel model shown in Figure 3. In this way, when the observer 4 determines the ground load on the unsprung member W, it estimates the displacement change rate of the road surface R and the displacement of the road surface R that cannot be directly observed by the sensor. In Figure 3, Mt is the unsprung mass of the unsprung member W, Ct is the viscous resistance coefficient of the tire, Kt is the spring constant of the tire, ft is the external force input to the unsprung member W, u is the control input, xt is the displacement of the unsprung member W, and xr is the road surface displacement.

The state equation of the unsprung member W in the one-wheel model shown in Figure 3 can be expressed by the following equation (2).

Here, the spring force of the suspension spring S and the damping force of the variable damper D, including the control input u, are regarded as disturbances, and the control input u is set to 0.

Furthermore, if the observed quantities are the vertical speed and displacement of the unsprung member W and the amount of deflection detected by the deflection amount detection unit 3, the output equation is expressed by the following equation (3).

Then, the system of the above-mentioned equations (2) and (3) is expanded to a system that includes disturbance as one of the states in addition to the state quantities, and the expanded system is regarded as a new system. Using the vertical velocity and displacement of the unsprung member W and the amount of tire deflection as observable quantities, an observer 4 is constructed that estimates the disturbance in addition to the state quantities. The state equation and output equation of the expanded system including disturbance can be expressed by the following equations (4) and (5).

Here, if the system of equations (2) and (3) is observable and the controllability matrix satisfies the rank condition, the extended system of equations (4) and (5) is also observable, making it possible to specify poles, and it is possible to configure observer 4 in the extended system as shown in the following equations (6) and (7).

When the vertical speed and displacement of the unsprung member W and the amount of tire deflection are input as observation quantities to the observer 4 configured in this manner, the observer 4 can estimate the vertical speed and displacement of the unsprung member W and the displacement change rate and displacement of the road surface R, and output the estimated vertical speed and estimated displacement of the unsprung member W, and the estimated displacement change rate and estimated displacement of the road surface R, respectively.

The ground load calculation unit 5 calculates the ground load fw of the unsprung member W based on the estimated vertical speed and estimated displacement of the unsprung member W estimated by the observer 4 and the estimated displacement change rate and estimated displacement of the road surface R.

Specifically, the ground load calculation unit 5 substitutes the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement rate of change and estimated displacement of the road surface R into the following formula (8), and calculates formula (8) to find the ground load fw of the unsprung member W.

As shown in the formula (8), the ground load calculation unit 5 calculates the ground load fw based on the tire spring constant Kt and viscous resistance constant Ct, but the tire spring constant Kt and viscous resistance coefficient Ct differ for each product depending on the product specifications. Therefore, the ground load estimation device 1 of this embodiment is provided with a setting unit 6 that sets the tire spring constant Kt and viscous resistance coefficient Ct. As described above, the tire spring constant Kt and viscous resistance coefficient Ct differ for each product depending on the product specifications, and the setting unit 6 is provided with a table (not shown) that associates the tire spring constant Kt and viscous resistance coefficient Ct with the product name, and an input device (not shown) that enables input of information (identification information) that can identify the tire, such as the product name and product number. When the user of the vehicle V inputs the tire identification information in the unsprung member W, the table is referenced and the tire spring constant Kt and viscous resistance coefficient Ct used in the calculation of the ground load calculation unit 5 are updated to values associated with the identification information. Therefore, when the user of the vehicle V replaces the tires, the ground load fw can be calculated using the spring constant Kt and viscous resistance coefficient Ct of the replaced tires, so the ground load estimation device 1 can accurately determine the ground load fw. Note that if the setting unit 6 does not have the above-mentioned table, the user may input the value of the spring constant Kt and the viscous resistance coefficient Ct as numerical values.

As shown in Figure 4, the ground load estimation device 1 configured in this manner detects the vertical acceleration of the unsprung member W by the acceleration sensor 21 while the vehicle V is traveling as an unsprung vibration detection step (step F1), and obtains the vertical speed and displacement of the unsprung member W by integrating and doubling the vertical acceleration of the unsprung member W detected by the acceleration sensor 21 (step F2). Next, as a deflection amount detection step, the ground load estimation device 1 retrieves information on the rotational speed of the wheels of the unsprung member W and the traveling speed of the vehicle V from the ECU in the vehicle V (step F3), linearly interpolates the rotational speed of the wheels and the traveling speed of the vehicle V, and substitutes the linearly interpolated wheel rotational speed and the traveling speed of the vehicle V into the equation for obtaining the deflection amount described above to obtain the deflection amount (step F4).

Next, as an estimated value calculation step, the ground load estimation device 1 inputs the vertical speed and displacement of the unsprung member W and the tire deflection amount obtained in steps F2 and F4 to the observer 4 as observed quantities to obtain the estimated speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R (step F5). Furthermore, as a ground load calculation step, the ground load estimation device 1 substitutes the estimated speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R into the formula for obtaining the ground load fw to obtain the ground load fw (step F6).

The ground load estimation device 1 may reverse the order of steps F1 and F2 and steps F3 and F4. In other words, the unsprung vibration detection step and the deflection amount detection step may be performed in reverse order. While the vehicle V is traveling, the ground load estimation device 1 repeatedly executes the above-mentioned steps F1 to F6 to determine the ground load fw for each calculation cycle.

...

As described above, the ground load estimation device 1 of this embodiment includes an unsprung vibration detection unit 2 that detects the vertical speed and displacement of the unsprung member W in the vehicle V, a deflection amount detection unit 3 that detects the vertical deflection amount of the tire in the unsprung member W, an observer 4 that receives the speed and displacement of the unsprung member W and the deflection amount of the tire as observation amounts and outputs the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R based on the state equation of the unsprung member W of the one-wheel model, and a ground load calculation unit 5 that calculates the ground load fw of the unsprung member W based on the estimated speed and estimated displacement of the unsprung member W estimated by the observer 4 and the estimated displacement change rate and estimated displacement of the road surface R.

In the ground load estimation device 1 configured in this manner, the speed and displacement of the unsprung member W and the amount of tire deflection are input to the observer 4 to obtain the road surface displacement change rate and road surface displacement required for obtaining the ground load fw. The rotation speed of the wheel in the unsprung member W and the speed of the vehicle V required for detecting the amount of tire deflection can be obtained from the vehicle V, and the only sensor required for the ground load estimation device 1 is the acceleration sensor 21 that detects the acceleration of the unsprung member W required for detecting the speed and displacement of the unsprung member W. Therefore, the ground load estimation device 1 of this embodiment can be manufactured at low cost. In addition, the ground load estimation device 1 uses the observer 4 that estimates the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R required for calculating the ground load fw based on the state equation of the unsprung member W of the one-wheel model, so that the ground load fw can be obtained accurately without requiring information on the external force acting on the sprung member B. As described above, the ground load estimation device 1 of this embodiment can estimate ground loads accurately and at low cost.

The ground load estimation program of this embodiment causes the computer to execute processing including an unsprung vibration detection step for detecting the vertical speed and displacement of the unsprung member W in the vehicle V, a deflection amount detection step for detecting the vertical deflection amount of the tire in the unsprung member W, an estimate value calculation step for inputting the speed and displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R as observed quantities to an observer 4 that outputs the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R based on the state equation of the unsprung member W of the one-wheel model, and a ground load calculation step for calculating the ground load fw of the unsprung member W based on the estimated speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R.

According to the ground load estimation program configured in this manner, the speed and displacement of the unsprung member W and the amount of tire deflection are input to the observer 4 to obtain the road surface displacement change rate and road surface displacement required for obtaining the ground load fw. The rotation speed of the wheel in the unsprung member W and the speed of the vehicle V required for detecting the amount of tire deflection can be obtained from the vehicle V, and the only sensor required for the ground load estimation device 1 is the acceleration sensor 21 that detects the acceleration of the unsprung member W required for detecting the speed and displacement of the unsprung member W. Therefore, if the ground load fw is obtained using the ground load estimation program of this embodiment, the ground load calculation device 1 that calculates the ground load fw can be manufactured at low cost. In addition, the ground load estimation program uses the observer 4 that estimates the estimated vertical speed and estimated displacement of the unsprung member W and the estimated displacement change rate and estimated displacement of the road surface R required for calculating the ground load fw based on the state equation of the unsprung member W of the one-wheel model, so that the ground load fw can be obtained accurately without requiring information on the external force acting on the sprung member B. As described above, the ground load estimation program of this embodiment allows for accurate estimation of ground load at low cost.

In addition, in the ground load estimation device 1 of this embodiment, the observer 4 is an observer of an extended system that regards all forces received from the sprung member B side of the vehicle V as disturbances. With the ground load estimation device 1 configured in this manner, the spring force of the suspension spring S and the damping force of the damping force variable damper D received from the sprung member B side are included in disturbances such as aerodynamic forces acting on the sprung member B, eliminating the need to input control input to the observer 4, and thus eliminating response delays due to control inputs, making it possible to calculate the ground load fw with even greater accuracy.

In addition, in the ground load estimation device 1 of this embodiment, the ground load calculation unit 5 calculates the ground load fw based on the tire spring constant Kt and viscous resistance constant Ct, and is equipped with a setting unit 6 that sets the spring constant Kt and the viscous resistance coefficient Ct. With the ground load estimation device 1 configured in this manner, the spring constant Kt and the viscous resistance coefficient Ct can be set to optimal values for the calculation of the ground load fw depending on the tire used in the unsprung member W of the vehicle V, so the ground load fw can be calculated with even greater accuracy.

Furthermore, the suspension device 10 in this embodiment is interposed between the sprung member B and the unsprung member W of the vehicle V and is capable of exerting a suppression force that suppresses the relative movement between the sprung member B and the unsprung member W in the vertical direction, and is equipped with a variable damping force damper (suppression force generating device) D that can change the suppression force, a controller C that controls the variable damping force damper (suppression force generating device) D, and a ground load calculation device 1, and the controller C controls the suppression force exerted by the variable damping force damper (suppression force generating device) D based on the ground load fw determined by the ground load estimation device 1.

The suspension device 10 configured in this manner is equipped with a ground load estimation device 1 that can estimate the ground load fw at low cost, making it possible to control the ground load at low cost.

In addition, according to the suspension device 10, the damping force variable damper (suppression force generating device) D exerts a suppression force based on the ground load fw, so that the damping force variable damper (suppression force generating device) D exerts a suppression force so that the ground load fw does not become equal to or less than a predetermined load, thereby suppressing the wheels of the unsprung member W from spinning while the vehicle V is traveling. In addition, according to the suspension device configured in this manner, since the ground load fw can be prevented from becoming equal to or less than a predetermined load, the inclination of the vehicle body posture in the sprung member B can be reduced when the vehicle V makes a sharp turn, brakes suddenly, or accelerates suddenly, thereby improving the ride comfort of the vehicle.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Ground load estimation device, 2: Unsprung vibration detection unit, 3: Deflection amount detection unit, 4: Observer, 5: Ground load calculation unit, 6: Setting unit, C: Controller, D: Variable damping force damper (suppression force generation device), V: Vehicle

Claims (5)

an unsprung vibration detection unit that detects a vertical speed and displacement of an unsprung member in a vehicle;
A deflection amount detection unit that detects a deflection amount of the unsprung member in a vertical direction of the tire;
an observer that receives the velocity and displacement of the unsprung member and the amount of deflection as observation quantities, and outputs an estimated velocity and estimated displacement of the unsprung member in a vertical direction and an estimated displacement rate of change and estimated displacement of the road surface based on a state equation of the unsprung member of a one-wheel model;
a ground load calculation unit that calculates a ground load of the unsprung member based on the estimated speed and estimated displacement of the unsprung member estimated by the observer, and the estimated displacement change rate and estimated displacement of the road surface. 2. The ground load estimation device according to claim 1, wherein the observer is an observer of an extended system that regards all forces acting from a vehicle body side of the vehicle as disturbances. the ground contact load calculation unit determines the ground contact load based on a spring constant and a viscous resistance constant of the tire;
The ground load estimation device according to claim 1, further comprising a setting unit that sets the value of the spring constant and the value of the viscous resistance coefficient. A suppression force generating device that is interposed between a sprung member and an unsprung member of the vehicle and is capable of exerting a suppression force that suppresses relative movement between the sprung member and the unsprung member in the vertical direction, and is capable of changing the suppression force;
A controller for controlling the suppression force generating device;
The ground load calculation device according to any one of claims 1 to 3,
The suspension device according to claim 1, wherein the controller controls the suppression force generated by the suppression force generation device based on the ground load determined by the ground load estimation device. On the computer,
an unsprung vibration detection step of detecting a vertical speed and displacement of an unsprung member in a vehicle;
a deflection amount detection step of detecting a deflection amount of the unsprung member in a vertical direction of the tire;
an estimate calculation step of inputting the velocity and displacement of the unsprung member and the deflection amount as observation quantities to an observer that outputs an estimated velocity and estimated displacement of the unsprung member in the vertical direction and an estimated displacement change rate and estimated displacement of the road surface based on a state equation of the unsprung member of a one-wheel model, and determining the estimated velocity and estimated displacement of the unsprung member and the estimated displacement change rate and estimated displacement of the road surface;
a ground load calculation step of calculating the ground load of the unsprung member based on the estimated speed and estimated displacement of the unsprung member, and the estimated displacement change rate and displacement of the road surface.

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