Ground load estimation device, suspension device, and ground load estimation program

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

Technical Field

[0001] The present invention relates to a ground load estimation device, a suspension device, and a ground load estimation program.

Background Art

[0002] In a conventional suspension device, for example, in order to prevent wheel spin during sudden acceleration of a vehicle, there is one that temporarily increases the ground load of the wheel. Such a suspension device includes an actuator interposed between the vehicle body and the wheel in the vehicle, and a controller that controls the actuator. When detecting sudden acceleration of the vehicle, it determines whether the wheel is in a spinning state, and if there is a possibility that the wheel will spin, it drives the actuator to temporarily increase the ground load of the wheel to prevent wheel spin (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in a conventional suspension device, when the wheel is likely to spin, the ground load of the wheel is increased, but the ground load itself of the wheel is not detected and the ground load cannot be grasped, so the ground load cannot be accurately controlled.

[0005] The ground load can theoretically be determined using equation (1) below by solving the equation of motion for the single-wheel model including the vehicle body and wheels shown in Figure 5. In equation (1), Mb represents the mass of the vehicle body 101 supported by one wheel (unsprung member) 100 in 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 travels, fb represents the external force acting on the vehicle body 101, Cs represents the damping coefficient of the base of a shock absorber 102 interposed between the vehicle body 101 and the wheel 100, Ks represents the spring constant of a suspension spring 103 interposed between the vehicle body 101 and the wheel 100, Ct represents the viscosity coefficient of the tire on the wheel 100, Kt represents the spring constant of the tire, and u represents a control command indicating the damping force adjustment applied to the damping force of the base of the shock absorber 102. In the formulas in this book, a variable with one dot above it represents the derivative of the variable, and a variable with two dots above it represents the second derivative of the variable.

[0006]

number

[0007] To determine 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, acceleration sensors must be attached to the suspension arms supporting the vehicle body 101 and the wheels 100, respectively. Furthermore, 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. Thus, determining the ground load requires at least two sensors, and furthermore, since external forces acting on the vehicle body 101 cannot be detected by the installation of sensors, the ground load cannot be accurately obtained.

[0008] Therefore, the present invention aims to provide a ground load estimation device capable of accurately estimating ground load at low cost, a ground load estimation program capable of accurately estimating ground load at low cost, and a suspension device capable of controlling ground load at low cost. [Means for solving the problem]

[0009] To achieve the above objective, the ground contact load estimation device in the problem-solving means of the present invention comprises: an unsprung vibration detection unit that detects the vertical velocity and displacement of the unsprung member in a vehicle; a deflection amount detection unit that detects the vertical deflection amount of the tire in the unsprung member; an observer that receives the velocity and displacement of the unsprung member and the deflection amount of the tire as observed quantities and outputs the estimated vertical velocity and estimated displacement of the unsprung member, and the estimated rate of change of the road surface and the estimated displacement based on the state equation of the unsprung member of a single-wheel model; and a ground contact load calculation unit that calculates the ground contact load of the unsprung member based on the estimated velocity and estimated displacement of the unsprung member and the estimated rate of change of the road surface and the estimated displacement estimated by the observer.

[0010] Furthermore, the ground contact load estimation program of the present invention causes a computer to execute a process that includes: an unsprung vibration detection step that detects the vertical velocity and displacement of the unsprung member in a vehicle; a deflection amount detection step that detects the vertical deflection amount of the tire in the unsprung member; an estimate value calculation step that inputs the velocity and displacement of the unsprung member and the deflection amount as observed quantities to an observer that outputs the estimated vertical velocity and displacement of the unsprung member and the estimated rate of change of the road surface and the estimated displacement based on the state equation of the unsprung member of a single-wheel model, and calculates the estimated velocity and displacement of the unsprung member and the estimated rate of change of the road surface and the estimated displacement; and a ground contact load calculation step that calculates the ground contact load of the unsprung member based on the estimated velocity, the estimated displacement, and the estimated rate of change of the road surface and the estimated displacement.

[0011] In the ground load estimation device and program configured in this way, the velocity and displacement of the unsprung member and the amount of tire deflection are input to the observer to determine the rate of change of road surface displacement and the displacement of the road surface necessary for determining the ground load. Therefore, the only sensor required to determine the ground load is an acceleration sensor that detects the acceleration of the unsprung member, which is necessary for detecting the velocity and displacement of the unsprung member. Furthermore, the ground load estimation device and program can accurately determine the ground load without requiring information on external forces acting on the sprung member.

[0012] Furthermore, the observer in the ground load estimation device may be an observer of an extended system that considers all forces received from the vehicle's sprung mass as disturbances. With a ground load estimation device configured in this way, by including the spring force of the suspension springs and the damping force of the variable damping damper received from the sprung mass as disturbances such as aerodynamics acting on the sprung mass, it becomes unnecessary to input control input to the observer. This eliminates response delays caused by control input, and allows for more accurate determination of the ground load.

[0013] Furthermore, in the ground load estimation device, the ground load calculation unit calculates the tire's spring constant and viscous resistance. Person in charge The device may also include a setting unit that determines the ground load based on the numbers and sets the spring constant and viscous resistance coefficient. With a ground load estimation device configured in this way, the spring constant and viscous resistance coefficient can be set to optimal values ​​for calculating the ground load according to the tires used as the unsprung member of the vehicle, thus enabling more accurate determination of the ground load.

[0014] The suspension system comprises a suppression force generating device interposed between the sprung mass and unsprung mass of the vehicle, capable of exerting a suppression force that suppresses the relative vertical movement between the sprung mass and unsprung mass, and capable of changing the suppression force; a controller that controls the suppression force generating device; and a ground load calculation device. 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. With a suspension system configured in this way, the ground load can be controlled at low cost because it is equipped with a ground load estimation device that can estimate the ground load at low cost. [Effects of the Invention]

[0015] Based on the 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 ground load can be controlled at low cost according to the suspension device of the present invention. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows a suspension system that utilizes a ground load estimation device in one embodiment. [Figure 2] This figure shows the configuration of a ground load estimation device according to one embodiment. [Figure 3] This diagram shows the unsprung mass of a vehicle in a single-wheel model. [Figure 4] This is a flowchart showing an example of the processing procedure for a ground load estimation device according to one embodiment. [Figure 5] This diagram shows the suprasprudence and unsprung mass in a single-wheel model. [Modes for carrying out the invention]

[0017] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. As shown in FIG. 1, the ground load estimation device 1 in the present embodiment estimates the ground load fw input to the controller C in the suspension device 10 interposed between the spring upper member B such as a vehicle body elastically supported by the suspension spring S in the vehicle V and the spring lower member W provided with wheels. The ground load fw is a vertical force acting on the spring lower member W in the vehicle V from the road surface R, and the controller C uses the ground load fw to obtain a restraining force generated in the damping force variable damper D in the suspension device 10.

[0018] Hereinafter, the ground load estimation device 1 and the suspension device 10 using the ground load estimation device 1 will be described in detail. First, the suspension device 10 is interposed between the spring upper member B and the spring lower member W of the vehicle V and can exert a restraining force that suppresses the vertical relative movement between the spring upper member B and the spring lower member W, and is a restraining force generating device capable of changing the restraining force. It includes a damping force variable damper D, a controller C that controls the damping force variable damper D, and a ground load estimation device 1. The vehicle V includes a suspension spring S that is interposed in parallel with the damping force variable damper D between the spring upper member B and the spring lower member W and elastically supports the spring upper member B.

[0019] Although not shown in detail, the damping force variable damper D includes a cylindrical outer shell, a piston movably inserted into the outer shell, and a piston rod axially movably inserted into the outer shell and connected to the piston. In addition, it can generate a damping force as a restraining force that suppresses the movement of the piston rod when the piston rod moves axially with respect to the outer shell, and includes a damping force adjustment valve that adjusts the damping force according to a command from the controller C. For the damping force adjustment valve, for example, a valve capable of changing the valve opening pressure and the flow passage area by supplying current is used.

[0020] In addition, when the liquid filled in the outer shell of the damping force variable damper D is an electro-viscous fluid or a magneto-viscous fluid, the damping force variable damper D may adjust the damping force up and down 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 the damping force adjustment valve. Further, the suppressing force generating device may be a hydraulic actuator or an electric actuator as long as it can exert a suppressing force that suppresses the relative movement in the vertical direction between the spring upper member B and the spring lower member W, and is not limited to a telescopic type damper or actuator, and may be a rotary type damper or actuator. Also, the suspension spring S is interposed in parallel with the damping force variable damper D between the spring upper member B and the spring lower member W, and elastically supports the spring upper member B.

[0021] In the suspension device 10, only one damping force variable damper D is shown in FIG. 1, but if the vehicle V is a four-wheel vehicle, it is provided at four locations between each of the four wheels and the vehicle body. The controller C does not necessarily need to be provided for each damping force variable damper D, and one controller C may control a plurality of damping force variable dampers D. Also, the controller C may control one damping force variable damper D in pairs with the damping force variable damper D. Note that the spring described between the spring lower member W and the road surface R in FIG. 1 indicates the spring element of the tire (not shown) in the spring lower member W. The vehicle V to which the ground load estimation device 1 and the suspension device 10 are applied is not limited to a four-wheel vehicle, and may be, for example, a two-wheel vehicle or a three-wheel vehicle.

[0022] 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 to indicate the target damping force that the variable damping force damper D should generate, and a drive circuit 12 that receives a command from the control unit 11 and supplies current to the damping force adjustment valve. For example, the control unit 11 generates an unsprung weight control command to prevent the ground load fw from falling below a predetermined load based on the ground load fw. The control unit 11 also generates a sprung weight control command that indicates the suppression force that the variable damping force damper D should generate to suppress vertical vibration of the sprung weight member B, based on the vertical acceleration of the sprung weight member B detected by the acceleration sensor 13 installed on the vehicle V. The control unit 11 then adds the unsprung weight control command and the sprung weight control command to determine the target damping force, and generates a current command that indicates the current to be supplied to the damping force adjustment valve so that the variable damping force damper D generates damping force according to the determined target damping force, and outputs it 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 Figure 2, and is unitized together with the drive circuit 12 in the controller C. Together with the drive circuit 12, it is attached as a single unit to the outer shell (not shown) of the variable damping force damper D. The variable damping force damper D has an outer shell connected to the unsprung member W and is interposed between the sprung member B and 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 variable damping force damper D, the acceleration sensor 21 can detect the vertical acceleration of the unsprung member W. Since the ground load estimation device 1 is equipped with an acceleration sensor 21, 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 obtain the sprung member control command.

[0023] The drive circuit 12 feeds back the current flowing to the damping force adjustment valve and supplies 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, and the processing of the control unit 11 described above is just one example; it can be arbitrarily modified as long as it generates a command to indicate the target damping force using the ground load fw.

[0024] As shown in Figure 2, the ground contact load estimation device 1 includes an unsprung vibration detection unit 2 that detects the vertical velocity 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 outputs the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R, and a ground contact load calculation unit 5 that calculates the ground contact load fw of the unsprung member W based on the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R estimated by the observer 4.

[0025] 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 and outputs 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 and outputs the vertical displacement of the unsprung member W. Note that the integrators 22 and 23 may each be pseudo-integral filters composed of high-pass filters, or they may obtain the integral value by performing an operation that sequentially adds the accelerations detected by the acceleration sensor 21.

[0026] The deflection detection unit 3 determines the amount of tire deflection in the unsprung member W based on the rotational speed of the wheel in the unsprung member W and the travel speed of the vehicle V. Specifically, the deflection detection unit 3 obtains information on the rotational speed of the unsprung member W and the travel speed of the vehicle V from an ECU (Electronic Control Unit) (not shown) in the vehicle V via a CAN (Controller Area Network) bus at a predetermined period, and determines the amount of tire deflection. Since the update period for updating the information on the rotational speed of the unsprung member W and the travel speed of the vehicle V obtained from the ECU is longer than the calculation period of the ground contact load estimation device 1, the deflection detection unit 3 estimates the current rotational speed and travel speed by linearly interpolating the rotational speed of the unsprung member W and the travel speed of the vehicle V at each calculation period from the time the rotational speed and travel speed were obtained until the next update of the rotational speed and travel speed. More specifically, assuming the update cycle is N times the calculation cycle, the value obtained by subtracting the rotational speed (traveling speed) from the rotational speed (traveling speed) obtained before last from the rotational speed (traveling speed) obtained before that, divided by N, is added to the previous rotational speed (traveling speed) at each calculation cycle to determine the rotational speed (traveling speed) used when the deflection amount detection unit 3 performs the calculation to determine the amount of tire deflection. 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 amount of tire deflection is dXtr, and the amount of tire deflection is Xtr, then Xtr(k) = Xtr(k-1) + dXtr(k) is calculated. However, dXtr(k) = -R{ω(k)-ω(k-1)} / V(k). Here, k represents time.

[0027] Furthermore, the deflection detection unit 3 processes the deflection amount Xtr(k) obtained by the aforementioned calculation formula with a high-pass filter at each calculation cycle to remove low-frequency components contained in the deflection amount, and then removes the offset and drift contained in the calculated deflection amount Xtr(k) to obtain the deflection amount Xtr.

[0028] Observer 4 uses the vertical velocity and displacement of the unsprung member W detected by the unsprung vibration detection unit 2, and the amount of deflection detected by the deflection detection unit 3. butWhen input as observed quantities, the observer 4 outputs the estimated vertical velocity and estimated displacement of the unsprung member W, as well as the estimated rate of change of displacement and estimated displacement of the road surface R, based on the state equation and output equation of the unsprung member W of the single-wheel model shown in Figure 3. In this way, the observer 4 estimates the rate of change of displacement and the displacement of the road surface R, which cannot be directly observed by the sensor, in order to determine the ground load on the unsprung member W. In Figure 3, Mt is the unsprung mass of the unsprung member W, Ct is the viscous drag 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.

[0029] The equation of state for the unsprung member W in the single-wheel model shown in Figure 3 can be expressed by the following equation (2).

[0030]

number

[0031] Here, the spring force of the suspension spring S and the damping force of the variable damping damper D, including the control input u, are considered as disturbances, and the control input u is set to 0.

[0032] Furthermore, if the observed quantities are the vertical velocity and displacement of the unsprung member W, and the amount of deflection detected by the deflection detection unit 3, the output equation can be expressed by the following equation (3).

[0033]

number

[0034] Then, the systems of equations (2) and (3) described above are extended to a system that includes disturbances as one of the states in addition to the state variables, and the extended system is considered as a new system. Observer 4 is constructed that estimates disturbances in addition to state variables, using the vertical velocity and displacement of the unsprung member W and the amount of tire deflection as observable quantities. The state equation and output equation of the extended system including disturbances can be expressed by the following equations (4) and (5).

[0035]

number

[0036] Here, if the systems of equations (2) and (3) are observable and the controllability matrix satisfies the rank condition, then the extended systems of equations (4) and (5) are also observable, allowing for pole specification, and observer 4 in the extended system can be constructed as shown in equations (6) and (7) below.

[0037]

number

[0038] When the vertical velocity and displacement of the unsprung member W and the amount of tire deflection are input to the observer 4 configured in this way, the observer 4 can estimate the vertical velocity and displacement of the unsprung member W and the rate of change of displacement and displacement of the road surface R, and output the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R, respectively.

[0039] The ground contact load calculation unit 5 calculates the ground contact load fw of the unsprung member W based on the estimated vertical velocity and estimated displacement of the unsprung member W estimated by the observer 4, and the estimated rate of change of displacement and estimated displacement of the road surface R.

[0040] Specifically, the ground load calculation unit 5 substitutes the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R into the following equation (8) and performs the calculation in equation (8) to obtain the ground load fw of the unsprung member W.

[0041]

number

[0042] The ground contact load calculation unit 5 calculates the tire's spring constant Kt and viscous resistance as shown in equation (8). Person in chargeThe ground contact load fw is determined based on a constant Ct, but the tire's spring constant Kt and viscous resistance coefficient Ct differ from product to product depending on the product specifications. Therefore, the ground contact load estimation device 1 of this embodiment is equipped with a setting unit 6 for setting the tire's spring constant Kt and viscous resistance coefficient Ct. As mentioned above, the tire's spring constant Kt and viscous resistance coefficient Ct differ from product to product depending on the product specifications, and the setting unit 6 is equipped with an out-of-figure table that associates the tire's spring constant Kt and viscous resistance coefficient Ct with the product name, and an out-of-figure input device that enables input of tire-identifying information such as the product name and product number. When the user of the vehicle V inputs the tire's identification information in the unsprung member W, the table is referenced and the tire's spring constant Kt and viscous resistance coefficient Ct used in the ground contact load calculation unit 5 are updated to the values ​​associated with the identification information. Therefore, when the user of vehicle V replaces the tires, the ground contact load fw can be calculated using the spring constant Kt and viscous resistance coefficient Ct of the replaced tires, so the ground contact load estimation device 1 can accurately determine the ground contact load fw. If the setting unit 6 does not have the aforementioned table, the user may input the values ​​of the spring constant Kt and the viscous resistance coefficient Ct numerically.

[0043] As shown in Figure 4, the ground load estimation device 1, configured in this way, detects the vertical acceleration of the unsprung member W using an acceleration sensor 21 while the vehicle V is in motion as an unsprung vibration detection step (step F1), and integrates and double integrates the vertical acceleration of the unsprung member W detected by the acceleration sensor 21 to obtain the vertical velocity and displacement of the unsprung member W (step F2). Subsequently, as a deflection detection step, the ground load estimation device 1 takes information on the rotational speed of the wheels on the unsprung member W and the travel speed of the vehicle V from the ECU in the vehicle V (step F3), linearly interpolates the rotational speed of the wheels and the travel speed of the vehicle V, and substitutes the linearly interpolated rotational speed of the wheels and the travel speed of the vehicle V into the aforementioned formula for determining the deflection amount to obtain the deflection amount (step F4).

[0044] Next, as an estimation step, the ground load estimation device 1 inputs the vertical velocity and displacement of the unsprung member W and the amount of tire deflection obtained in steps F2 and F4 as observed quantities to the observer 4 to obtain the estimated velocity and estimated displacement of the unsprung member W, and the estimated rate of change of displacement 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 velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R into the formula for calculating the ground load fw to obtain the ground load fw (step F6).

[0045] The ground load estimation device 1 may perform the processes in steps F1 and F2 in the reverse order of the processes in steps F3 and F4. In other words, the unsprung vibration detection step and the deflection amount detection step may be performed in the reverse order. While the vehicle V is in motion, the ground load estimation device 1 repeatedly performs the processes from step F1 to step F6 described above to determine the ground load fw at each calculation cycle.

[0046] Excluding the acceleration sensor 21, the hardware resources of the ground load estimation device 1, although not shown in the diagram, specifically include, for example, an interface for receiving signals from the acceleration sensor 21 and an ECU (not shown), an input device in the setting unit 6, a storage device such as a ROM (Read Only Memory) that stores a program used for processing necessary to determine the ground load fw, a computing device such as a CPU (Central Processing Unit) that executes processing based on the program, and a storage device such as a RAM (Random Access Memory) that provides a memory area to the CPU. Each part of the ground load estimation device 1 can be realized by the execution of the program by the CPU. The controller C may also be realized by utilizing the hardware resources of the ground load estimation device 1. In that case, the program necessary for processing in the controller C can be stored in the storage device, and each part of the controller C can be realized by the execution of the program by the CPU.

[0047] As described above, the ground contact load estimation device 1 of this embodiment comprises: an unsprung vibration detection unit 2 that detects the vertical velocity 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 velocity and displacement of the unsprung member W and the deflection amount of the tire as observed quantities and outputs the estimated vertical velocity and estimated displacement of the unsprung member W, and the estimated rate of change of displacement and estimated displacement of the road surface R, based on the state equation of the unsprung member W of a single-wheel model; and a ground contact load calculation unit 5 that calculates the ground contact load fw of the unsprung member W based on the estimated velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R estimated by the observer 4.

[0048] In the ground load estimation device 1 configured in this way, the velocity and displacement of the unsprung member W and the amount of tire deflection are input to the observer 4 to determine the rate of change of the road surface displacement and the displacement of the road surface necessary for determining the ground load fw. The rotational speed of the wheel in the unsprung member W and the speed of the vehicle V, which are necessary 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 which detects the acceleration of the unsprung member W, which is necessary for detecting the velocity and displacement of the unsprung member W. Therefore, the ground load estimation device 1 of this embodiment can be manufactured at low cost. Furthermore, since the ground load estimation device 1 utilizes the observer 4 which estimates the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of the road surface R and the estimated displacement, which are necessary for calculating the ground load fw, based on the state equation of the unsprung member W of a single-wheel model, it does not require information on external forces acting on the sprung member B and can accurately determine the ground load fw. Based on the above, the ground load estimation device 1 of this embodiment can estimate the ground load accurately at low cost.

[0049] Furthermore, the ground contact load estimation program of this embodiment causes a computer to execute a process that includes: an unsprung vibration detection step that detects the vertical velocity and displacement of the unsprung member W in the vehicle V; a deflection detection step that detects the vertical deflection amount of the tire in the unsprung member W; an observer 4 that outputs the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R based on the state equation of the unsprung member W of a single-wheel model, inputting the velocity and displacement of the unsprung member W and the deflection amount as observed quantities, and calculating estimated values ​​to obtain the estimated velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R; and a ground contact load calculation step that calculates the ground contact load fw of the unsprung member W based on the estimated velocity and estimated displacement of the unsprung member W and the estimated rate of change of displacement and estimated displacement of the road surface R.

[0050] According to the ground load estimation program configured in this way, the velocity and displacement of the unsprung member W and the amount of tire deflection are input to the observer 4 to determine the rate of change of the road surface displacement and the displacement of the road surface necessary for determining the ground load fw. The rotational speed of the wheel in the unsprung member W and the speed of the vehicle V, which are necessary 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 which detects the acceleration of the unsprung member W, which is necessary for detecting the velocity and displacement of the unsprung member W. Therefore, by using the ground load estimation program of this embodiment to determine the ground load fw, the ground load calculation device 1 for determining the ground load fw can be manufactured at low cost. Furthermore, since the ground load estimation program utilizes the observer 4 which estimates the estimated vertical velocity and estimated displacement of the unsprung member W and the estimated rate of change of the road surface R and the estimated displacement, which are necessary for calculating the ground load fw, based on the state equation of the unsprung member W of a single-wheel model, it does not require information on external forces acting on the sprung member B and can determine the ground load fw with high accuracy. Based on the above, the ground load estimation program of this embodiment can estimate the ground load accurately at low cost.

[0051] Furthermore, in the ground contact load estimation device 1 of this embodiment, the observer 4 is an observer of an extended system that considers all forces received from the sprung mass B side of the vehicle V as disturbances. With the ground contact load estimation device 1 configured in this way, by including the spring force of the suspension spring S and the damping force of the variable damping damper D received from the sprung mass B side as disturbances such as aerodynamics acting on the sprung mass B, it becomes unnecessary to input control input to the observer 4, thus eliminating response delays caused by control input and allowing the ground contact load fw to be determined with even greater accuracy.

[0052] Furthermore, in the ground load estimation device 1 of this embodiment, the ground load calculation unit 5 calculates the spring constant Kt and viscous resistance of the tire. Person in charge The device includes a setting unit 6 that determines the ground load fw based on a number Ct and sets the spring constant Kt and the viscous resistance coefficient Ct. With the ground load estimation device 1 configured in this way, the spring constant Kt and the viscous resistance coefficient Ct can be set to optimal values ​​for calculating the ground load fw according to the tire used in the unsprung member W of the vehicle V, so the ground load fw can be determined with even greater accuracy.

[0053] Furthermore, the suspension device 10 in this embodiment includes a damping force variable damper (suppression force generating device) D interposed between the sprung mass B and the unsprung mass W of the vehicle V, capable of exerting a suppression force that suppresses the relative vertical movement between the sprung mass B and the unsprung mass W, and capable of changing the suppression force; a controller C that controls the damping force variable damper (suppression force generating device) D; and a ground contact load calculation device 1. The controller C controls the suppression force exerted by the damping force variable damper (suppression force generating device) D based on the ground contact load fw determined by the ground contact load estimation device 1.

[0054] With the suspension device 10 configured in this way, it is equipped with a ground load estimation device 1 that can estimate the ground load fw at low cost, and therefore the ground load can be controlled at low cost.

[0055] Furthermore, the suspension system 10 controls the suppression force exerted by the variable damping damper (suppression force generating device) D based on the ground load fw, so that the variable damping damper (suppression force generating device) D exerts a suppression force so that the ground load fw does not fall below a predetermined load, thereby suppressing the wheels on the unsprung member W from slipping while the vehicle V is in motion. In addition, with a suspension system configured in this way, it is possible to prevent the ground load fw from falling below a predetermined load, so that when the vehicle V makes a sharp turn, brakes suddenly, or accelerates suddenly, the tilt of the vehicle body on the sprung member B is reduced, thereby improving the ride comfort of the vehicle.

[0056] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims. [Explanation of symbols]

[0057] 1. Ground load estimation device, 2. Unsprung vibration detection unit, 3. Deflection detection unit, 4. Observer, 5. Ground load calculation unit, 6. Setting unit, C. Controller, D. Variable damping force damper (suppression force generating device), V. Vehicle

Claims

1. A suspension vibration detection unit that detects the vertical velocity and displacement of the unsprung member in a vehicle, A deflection amount detection unit for detecting the amount of vertical deflection of the tire in the unsprung member, An observer receives the velocity, displacement, and deflection of the unsprung member as input values, and outputs the estimated vertical velocity and displacement of the unsprung member, and the estimated rate of change of the road surface displacement and the estimated displacement, based on the equation of state of the unsprung member of a single-wheel model. The system includes a ground load calculation unit that calculates the ground load of the unsprung member based on the estimated velocity and estimated displacement of the unsprung member estimated by the observer, and the estimated rate of change of displacement and estimated displacement of the road surface. A ground load estimation device characterized by the following features.

2. The aforementioned observer is an observer of an extended system that considers all forces received from the vehicle body as disturbances. The ground load estimation device according to feature 1.

3. The ground contact load calculation unit determines the ground contact load based on the spring constant and viscous resistance coefficient of the tire, The system includes a setting unit for setting the value of the spring constant and the value of the viscous resistance coefficient. The ground load estimation device according to feature 1.

4. A suppression force generating device interposed between the sprung mass and the unsprung mass of the vehicle, capable of exerting a suppression force that suppresses relative vertical movement between the sprung mass and the unsprung mass, and capable of changing the suppression force; A controller that controls the suppression force generating device, The device comprises a ground load calculation device according to any one of claims 1 to 3, The controller controls the suppression force exerted by the suppression force generating device based on the ground load estimation device. A suspension device characterized by the following features.

5. On the computer, A step for detecting unsprung vibration in a vehicle, which detects the vertical velocity and displacement of the unsprung member, A deflection amount detection step for detecting the amount of vertical deflection of the tire in the unsprung member, An estimate calculation step is performed to input the velocity and displacement of the unsprung member and the amount of deflection of the unsprung member as observed quantities to an observer that outputs the estimated vertical velocity and displacement of the unsprung member and the estimated rate of change of the road surface and the estimated displacement based on the state equation of the unsprung member of a single-wheel model, and to calculate the estimated velocity and displacement of the unsprung member and the estimated rate of change of the road surface and the estimated displacement of the road surface. The process includes a ground load calculation step that calculates the ground load of the unsprung member based on the estimated velocity and estimated displacement of the unsprung member and the estimated rate of change of displacement and displacement of the road surface. A ground load estimation program characterized by the following:

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