JP7765263B2 - Vibration information estimation device and suspension device - Google Patents

Description

The present invention relates to a vibration information estimation device and a suspension device.

In a suspension system equipped with a variable damping force shock absorber interposed between the vehicle body and wheels, with the aim of improving ride comfort, and a control device that controls the control force exerted by the shock absorber in accordance with the skyhook control law, it is necessary to detect the vertical speed of the vehicle body and the stroke speed of the suspension system.

The vertical velocity of the vehicle body can be obtained by integrating the vertical acceleration of the vehicle body detected by an acceleration sensor installed on the vehicle body. Furthermore, the stroke velocity can be obtained by installing a stroke sensor that detects the relative displacement between the vehicle body and the wheels, detecting the stroke displacement, and differentiating the stroke displacement, or by installing acceleration sensors that detect the vertical acceleration on both the vehicle body and the wheels, integrating the detected accelerations of both the vehicle body and the wheels, and then finding the difference between the two to obtain the stroke velocity.

In this way, at least two sensors are required to obtain the vehicle body's vertical speed and stroke speed, which not only makes the control device for the shock absorber expensive, but also requires space to install the sensors, so there is a demand for an inexpensive, space-saving control device.

To meet this demand, one proposal is to apply a vibration information estimation device to a control device that uses a single-wheel model observer that estimates stroke displacement as a state quantity, with the observed quantity being the vehicle's vertical acceleration. With a vibration information estimation device configured in this way, only one acceleration sensor is required to estimate the stroke displacement between one wheel and the vehicle body, making the control device inexpensive and space-saving.

Specifically, the vibration information estimation device incorporates the shock absorber's nonlinear characteristics in the form of a map into the observer model, and performs compensation to maintain the observer gain at an appropriate value depending on the shock absorber's damping coefficient or the magnitude of the control command given to the shock absorber's damping valve, thereby improving the accuracy of stroke displacement estimation (see, for example, Patent Document 1).

JP 2019-31125 A

However, conventional vibration information estimation devices estimate stroke displacement using a single-wheel model observer, and therefore do not take into account the lateral roll of the vehicle body.

As a result, for example, when a four-wheeled vehicle travels on a sinusoidal road where the left and right wheels are in opposite phase, the phase of the estimated stroke displacement on the rear wheels lags behind the actual measured value due to the effect of the vehicle body roll that occurs when the front wheels travel on the sinusoidal road.

As a result, conventional vibration information estimation devices find it difficult to accurately estimate vibration information such as stroke displacement and stroke speed, and suspension devices that use vibration information estimated by a vibration information estimation device are unable to effectively suppress vehicle body vibration due to errors between the actual measured and estimated vibration information values, meaning that further improvements in vehicle ride comfort are desired.

Therefore, an object of the present invention is to provide a vibration information estimation device that can accurately estimate vibration information on the rear wheel side relative to the vehicle's traveling direction, and another object is to provide a suspension device that can improve ride comfort in the vehicle.

The vibration information estimation device in the problem-solving means of the present invention is configured to include a roll acceleration detection unit that detects roll acceleration, which is the acceleration in the roll direction of the body of a vehicle having wheels on the front, rear, left and right sides; a vertical acceleration detection unit that detects vertical acceleration, which is the acceleration in the up and down direction of the body directly above the rear wheels in the direction of travel of the vehicle; a correction unit that corrects the vertical acceleration based on the roll acceleration of the front wheels in the direction of travel of the vehicle ; and an observer that uses the vertical acceleration corrected by the correction unit as input and estimates relative vibration information in the up and down direction between the body and rear wheels of the vehicle based on a state equation of a single wheel model.

The vibration information estimation device configured in this manner is equipped with a correction unit that corrects the vertical acceleration based on the roll acceleration of the front wheels in the direction of vehicle travel , making it possible to remove from the vertical acceleration the acceleration component due to roll that interferes with the observer's estimation of stroke displacement.

The correction unit in the vibration information estimation device may also correct the vertical acceleration detected when the rear wheels pass over the same road surface as the front wheels in the vehicle's traveling direction, based on the roll acceleration obtained when the front wheels pass over the same road surface. With a vibration information estimation device configured in this way, when the front and rear wheels pass over the same road surface, the vertical acceleration can be corrected using the roll angular velocity obtained when the front wheels travel on the same road surface, allowing for more accurate estimation of vibration information.

The suspension system may further include a shock absorber with adjustable damping force or an actuator with adjustable thrust force interposed between the vehicle body and the rear wheels, a control device for controlling the shock absorber or actuator, and a vibration information estimation device, and the control device may control the shock absorber or actuator based on vibration information estimated by the vibration information estimation device. A suspension system configured in this manner can control the shock absorber or actuator based on accurately estimated vibration information, thereby effectively suppressing vibrations in the vehicle body and improving ride comfort.

The vibration information estimation device of the present invention can accurately estimate vibration information on the rear wheel side relative to the vehicle's traveling direction. Furthermore, the suspension device of the present invention can improve the ride comfort of the vehicle.

1 is a diagram showing a suspension device according to an embodiment mounted on a vehicle; 1 is a diagram illustrating a configuration of a vibration information estimation device according to an embodiment. FIG. 1 is a diagram illustrating a configuration of a control device in a suspension device according to an embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of a vibration information estimation device and a control device according to an embodiment. FIG. 2 is a diagram showing the configuration of a processing unit that performs processing of the vibration information estimation device and the control device. FIG. 1 is a diagram showing a one-wheel model of a vehicle. 1 is a flowchart showing a processing procedure of a vibration information estimation device according to an embodiment.

The present invention will now be described based on the embodiments shown in the drawings. As shown in Figures 1 and 2, the vibration information estimation device 1 includes a roll acceleration detection unit 2 that detects roll acceleration φ, which is the acceleration in the roll direction of a vehicle body B of a vehicle V having front, rear, left, and right wheels Wfl, Wfr, Wrl, and Wrr; a vertical acceleration detection unit 3 that detects vertical accelerations αzrl, αzrr, which are the vertical accelerations of the vehicle body B directly above the rear wheels Wrl, Wrr in the direction of travel of the vehicle V; a correction unit 4 that corrects the vertical acceleration based on the roll acceleration φ; and an observer 5 that uses the vertical accelerations αzrl, αzrr corrected by the correction unit 4 as input and estimates stroke displacements Xl, Xr as relative vertical vibration information between the vehicle body B and the rear wheels Wrl, Wrr of the vehicle V based on a state equation of a single-wheel model. Note that the vibration information may be any information that can grasp the relative vibration between the vehicle body B and the rear wheels Wrl, Wrr, such as stroke displacement, which is the relative displacement in the vertical direction between the two, as well as the relative speed or relative acceleration between the two. Furthermore, the front and rear of the vehicle V are defined based on the direction of travel of the vehicle V, with the wheels located in front of the direction of travel of the vehicle V being referred to as the front wheels, and the wheels located behind the direction of travel of the vehicle V being referred to as the rear wheels.

Furthermore, as shown in Figures 1 and 3, the suspension device Sd of this embodiment includes a shock absorber D with adjustable damping force that is interposed between the vehicle body B and the rear wheels Wrl, Wrr, a control device C that controls the shock absorber D, and a vibration information estimation device 1, and the control device C controls the shock absorber D based on the stroke displacement, which is vibration information obtained by the vibration information estimation device 1.

As shown in FIG. 3, the control device C includes a stroke displacement estimation device 30 that estimates the stroke displacement between the vehicle body B and the front wheels Wfl, Wfr; a target damping force calculation unit 20 that calculates the target damping forces Ffl, Ffr, Frl, Frr using the stroke displacement of the front wheels Wfl, Wfr estimated by the stroke displacement estimation device 30 and the stroke displacement of the rear wheels Wrl, Wrr estimated by the vibration information estimation device 1; and a command current determination unit 21 that calculates the target currents Ifl, Ifr, Irl, Irr to be supplied from the target damping forces Ffl, Ffr, Frl, Frr to the damping force adjustment units F of the dampers D for each of the four wheels Wfl, Wfr, Wrl, Wrr.

Vehicle V is equipped with suspension springs S, which are interposed in parallel with shock absorbers D between vehicle body B and the front, rear, left, and right wheels Wfl, Wfr, Wrl, and Wrr of vehicle body B, and vehicle body B is elastically supported by the suspension springs S. Although not shown in detail, shock absorbers D are equipped with damping force adjustment units F internally, and the damping force can be changed in response to the current supplied to the damping force adjustment units F by a control device C. In this manner, the damping force of shock absorbers D is controlled by the control device C. Damping force adjustment units F are, for example, solenoid valves that adjust the opening area or valve opening pressure in response to the supplied current. Note that damping force adjustment units F may also be a valve unit equipped with a damping valve and a solenoid valve that adjusts the back pressure that urges the valve element of the damping valve toward the valve seat.

As shown in FIG. 4, the vibration information estimation device 1 includes, as hardware, acceleration sensors 10, 11, and 12 that are mounted on vehicle body B and detect vertical acceleration at their installation positions on vehicle body B, and a processing unit 13 that performs processing to estimate vibration information from the acceleration detected by the acceleration sensors 10, 11, and 12. The various components of the vibration information estimation device 1 are realized by the processing of the processing unit 13. Furthermore, the control device C in the suspension device Sd of this embodiment shares some of its hardware with the vibration information estimation device 1, and includes the acceleration sensors 10, 11, and 12 and a processing unit 13 that performs processing to determine the target damping force to be generated by the shock absorber D, and a drive circuit 14 that supplies current to the damping force adjustment unit F in response to commands from the processing unit 13.

As shown in FIG. 5, the arithmetic processing device 13 includes a CPU (Central Processing Unit) 13a, a memory 13b that stores programs for the CPU 13a to perform processing as the vibration information estimation device 1 and the control device C and provides the storage area necessary for CPU 13a's processing, an interface 13c that enables signal exchange between the CPU 13a, memory 13b, acceleration sensors 10, 11, and 12, and drive circuit 14, and a bus 13d that communicatively connects these devices to one another. The drive circuit 14 is provided for each of the four shock absorbers D interposed between the vehicle body B and each of the four wheels Wfl, Wfr, Wrl, and Wrr of the vehicle V, and supplies a current of a value specified by the command to the damping force adjustment unit F in response to a command from the arithmetic processing device 13. The drive circuit 14 may be, for example, a drive circuit other than one that performs PWM drive.

The CPU 13a processes the vertical accelerations _α1 , _α2 , and _α3 of the vehicle body B detected by the acceleration sensors 10, 11, and 12 by executing the operating system and other programs, and also controls the memory 13b. The memory 13b includes a ROM (Read Only Memory) and a RAM (Random Access Memory) that provides a storage area necessary for the arithmetic processing of the CPU 13a, and the programs used for the arithmetic processing of the CPU 13a are stored in the ROM. Note that the programs used for the arithmetic processing of the CPU 13a may be stored in a storage device other than the memory 13b, and may be read into the RAM in the memory 13b at the time of execution and executed on the RAM.

Each component of the vibration information estimation device 1 will be described in detail below. The roll acceleration detection unit 2 detects roll acceleration φ, which is the acceleration of the vehicle body B in the roll direction. Furthermore, the vertical acceleration detection unit 3 detects vertical accelerations αzrl, αzrr, which are the accelerations of the vehicle body B in the vertical direction directly above the rear wheels Wrl, Wrr in the traveling direction of the vehicle V. The roll acceleration detection unit 2 and the vertical acceleration detection unit 3 include three acceleration sensors 10, 11, 12 installed on the vehicle body B, and detect the roll acceleration φ and the vertical accelerations αzrl, αzrr, which are the accelerations in the roll direction of the vehicle body B, from the vertical accelerations _α1 , _α2 , _α3, which are the accelerations in the vertical direction at three locations on the vehicle body B detected by these acceleration sensors 10, 11, 12. More specifically, the processing in the roll acceleration detection unit 2 and the vertical acceleration detection unit 3 is realized by the calculation processing unit 13 processing the accelerations _α1 , _α2 , _α3 .

The three acceleration sensors 10, 11, and 12 are installed at three arbitrary locations that are not on the same straight line in the front-to-back or left-to-right directions of the vehicle body B, and each detects the vertical accelerations _α1 , _α2 , and _α3 of the vehicle body B at the installation location.

The calculation processing device 13 determines the vertical accelerations αzrl, αzrr directly above the rear wheels Wrl, Wrr of the vehicle body B from the accelerations _α1 , _α2 , _α3 detected by the acceleration sensors 10, 11, 12. Specifically, the calculation processing device 13 regards the vehicle body B as a rigid body and obtains the vertical accelerations of any three locations that are not on the same line in the fore-aft or lateral directions of the vehicle body B, thereby obtaining the accelerations in the vertical direction, fore-aft rotation, and lateral rotation of the vehicle body B. Therefore, from these accelerations, the calculation processing device 13 determines the bounce acceleration, which is the vertical acceleration at the center of gravity of the vehicle body B, the pitch acceleration, which is the angular acceleration of the fore-aft rotation at the center of gravity, and the roll acceleration φ, which is the angular acceleration of the lateral rotation at the center of gravity.

After calculating the bounce acceleration, pitch acceleration, and roll acceleration φ, the calculation processing device 13 uses the tread value Lt of the rear wheels Wrl and Wrr and the wheelbase value Lh to calculate the vertical accelerations αzrl and αzrr of the vehicle body B immediately above the rear wheels Wrl and Wrr. If the roll acceleration in the direction in which the vehicle body B rotates to the left relative to the vehicle's direction of travel is considered positive, the vertical acceleration αzrl of the vehicle body B immediately above the rear wheel Wrl is calculated by adding the bounce acceleration value, the pitch acceleration multiplied by Lh/2, and the roll acceleration φ multiplied by Lt/2. Furthermore, the vertical acceleration αzrr of the vehicle body B immediately above the rear wheel Wrr is calculated by subtracting the roll acceleration φ multiplied by Lt/2 from the sum of the bounce acceleration value and the pitch acceleration multiplied by Lh/2.

In this way, the arithmetic processing device 13 processes the accelerations _α1 , _α2 , and _α3 detected by the acceleration sensors 10, 11, and 12 to perform processing as the roll acceleration detection unit 2 and the vertical acceleration detection unit 3. The arithmetic processing device 13 detects the roll acceleration φ and the vertical accelerations αzrl and αzrr directly above the rear wheels Wrl and Wrr at a predetermined sampling period. The arithmetic processing device 13 also stores the determined roll acceleration φ in the memory 13b. The memory 13b has an area for storing the roll acceleration φ determined over a period of several seconds, and when the area becomes full, the values of the roll acceleration φ in the memory 13b are updated by sequentially overwriting the oldest roll acceleration φ with the newest roll acceleration φ.

When an acceleration sensor is used to detect the vertical acceleration of the vehicle body B immediately above the rear wheels Wrl, Wrr, the acceleration detected by the acceleration sensor is the vertical accelerations αzrl, αzrr immediately above the rear wheels Wrl, Wrr, and therefore these acceleration sensors may be used to configure the vertical acceleration detection unit 3. Also, when an acceleration sensor is used to directly detect the vertical accelerations αzrl, αzrr immediately above the rear wheels Wrl, Wrr, the arithmetic processing unit 13 may divide the difference between the vertical accelerations αzrl, αzrr by the tread value Lt between the rear wheels Wrl, Wrr to obtain the roll acceleration φ of the vehicle body B, thereby realizing the roll acceleration detection unit 2. Furthermore, as will be described later, the suspension device Sd of this embodiment needs to detect the vertical accelerations αzfl, αzfr, αzrl, αzrr of the vehicle body B directly above the four wheels Wfl, Wfr, Wrl, Wrr in order to control the dampers D of the four wheels Wfl, Wfr, Wrl, Wrr. Therefore, acceleration sensors may be installed at four locations on the vehicle body B directly above the four wheels Wfl, Wfr, Wrl, Wrr, and the four acceleration sensors may detect the vertical accelerations αzfl, αzfr, αzrl, αzrr of the vehicle body B directly above the four wheels Wfl, Wfr, Wrl, Wrr. However, by processing the accelerations _α1 , _α2 , _α3 detected by the three acceleration sensors 10, 11, 12 to determine the bounce acceleration, pitch acceleration, and roll acceleration φ, the vertical accelerations αzfl, αzfr, αzrl, αzrr of the vehicle body B directly above the four wheels Wfl, Wfr, Wrl, Wrr can be determined, which means that one fewer acceleration sensor needs to be installed, making the suspension device Sd less expensive.

In addition, if the vehicle V is equipped with an acceleration sensor that detects the vertical acceleration of the vehicle body B, separate from the vibration information estimation device 1, the vertical accelerations αzfl, αzfr, αzrl, αzrr of the vehicle body B directly above the front wheels Wfl, Wfr and rear wheels Wrl, Wrr may be obtained from the vehicle V via a CAN (Controller Area Network) bus or an on-board diagnosis (OBD) installed in the vehicle V.

The correction unit 4 next includes a correction value calculation unit 4a that calculates a correction value based on the roll acceleration φ and the speed v of the vehicle V, and an adder/subtractor 4b that calculates corrected vertical accelerations αzrla, αzrra based on the vertical accelerations αzrl, αzrr of the vehicle body B directly above the rear wheels Wrl, Wrr and the correction value calculated by the correction value calculation unit 4a. The speed v of the vehicle V is generally information detected by the vehicle V, so it may be obtained from the vehicle V via the CAN bus or OBD. However, as shown in Figure 2, the speed v may also be obtained by providing a speed sensor 7 that detects the speed v of the vehicle V.

Specifically, the processing of each part of correction unit 4 is executed by arithmetic processing device 13. Arithmetic processing device 13 processes speed sensor 7, which detects speed v of vehicle V, roll acceleration φ detected by roll acceleration detection unit 2, and speed v detected by speed sensor 7, to correct the vertical acceleration of vehicle body B directly above rear wheels Wrl, Wrr. In this way, by executing the above processing, arithmetic processing device 13 realizes correction unit 4, which corrects the vertical acceleration of vehicle body B directly above rear wheels Wrl, Wrr.

Assuming that, while vehicle V is traveling, rear wheels Wrl, Wrr pass over the same road surface as front wheels Wfl, Wfr in the direction of vehicle V's travel, correction unit 4 corrects the vertical accelerations αzrl, αzrr detected when rear wheels Wrl, Wrr pass over the same road surface based on roll acceleration φ acquired when front wheels Wfl, Wfr pass over the same road surface. In other words, correction unit 4 performs processing to remove from vertical accelerations αzrl, αzrr of rear wheels Wrl, Wrr the influence of roll acceleration φ of vehicle body B that would occur when rear wheels Wrl, Wrr pass over the same road surface as front wheels Wfl, Wfr.

When vehicle V is traveling and its front wheels Wfl, Wfr reach and pass over a certain road surface, if vehicle V continues straight ahead, the rear wheels Wrl, Wrr, which are located behind the front wheels Wfl, Wfr and on the same line along the fore-and-aft direction of vehicle V, will pass over the same road surface as the front wheels Wfl, Wfr after a certain number of seconds. If vehicle V's speed v is constant, the wheelbase value Lh, which is the distance between vehicle V's front wheels Wfl, Wfr and rear wheels Wrl, Wrr, is known, so the delay time t from when the front wheels Wfl, Wfr pass over a certain road surface until the rear wheels Wfl, Wfr reach the same road surface, can be found by calculating Lh/v. If the speed v of vehicle V changes after the front wheels Wfl, Wfr pass over a road surface, speed v is monitored. The point at which the integrated value of speed v after the front wheels Wfl, Wfr pass over the road surface equals the wheelbase value Lh is the point at which the rear wheels Wrl, Wrr reach the same road surface. By making the above assumptions, it is possible to determine how many seconds before the rear wheels Wrl, Wrr reach the same road surface that the front wheels Wfl, Wfr pass over the same road surface. Furthermore, since the roll acceleration φ of vehicle body B when the rear wheels Wrl, Wrr pass over the same road surface as the front wheels Wfl, Wfr is expected to be similar to the roll acceleration when the front wheels Wfl, Wfr pass over the same road surface, the roll acceleration φ when the front wheels Wfl, Wfr pass over the same road surface can be estimated as the roll acceleration φ when the rear wheels Wrl, Wrr pass over the same road surface.

From the above, the correction value calculation unit 4a calculates the delay time t from the time when the front wheels Wfl, Wfr pass over a certain road surface to the time when the rear wheels Wrl, Wrr are expected to pass over the same road surface, based on the speed v of the vehicle V and the wheelbase value Lh. As described above, when the rear wheels Wrl, Wrr are expected to pass over the same road surface as the front wheels Wfl, Wfr, the roll acceleration φ obtained at the time t before can be considered to be the roll acceleration when the rear wheels Wrl, Wrr pass over the same road surface. Therefore, the correction value calculation unit 4a calculates the roll acceleration component included in the vertical accelerations αzrl, αzrr as the correction _value αφ using the roll acceleration φ obtained at the time t before. Specifically, the arithmetic processing device 13 calculates the correction value _αφ = φ × (Lt/2) to obtain the acceleration component, thereby realizing the correction value calculation unit 4a. Furthermore, the adder-subtractor 4b adds the correction _{value αφ} to the vertical acceleration αzrl of the vehicle body B immediately above the left rear wheel Wrl to remove the acceleration component due to roll contained in the vertical acceleration αzrl of the vehicle body B immediately above the left rear wheel Wrl, and subtracts the correction _value αφ obtained time t earlier from the vertical acceleration αzrr of the vehicle body B immediately above the right rear wheel Wrr to remove the acceleration component due to roll contained in the vertical acceleration αzrr of the vehicle body B immediately above the right rear wheel Wrr. The processing in the adder-subtractor 4b is also realized by the calculation processing device 13 performing the above-mentioned calculation processing. The correction unit 4 is thus realized by the calculation processing device 13 performing the above-mentioned calculation processing, and inputs the corrected vertical accelerations αzrla and αzrra to the observer 5. Here, αzrla = αzrl + _αφ , and αzrra = αzrr - _αφ .

Specifically, the calculation processing device 13 calculates the aforementioned time t from the vehicle V's speed v and the wheelbase value Lh, reads from memory 13b the value of roll acceleration φ obtained time t before the time point at which the corrected vertical accelerations αzrla and αzrra are calculated, and corrects the vertical accelerations αzrl and αzrr. Because the correction unit 4 requires the value of roll acceleration φ obtained time t before the time point at which the corrected vertical accelerations αzrla and αzrra are calculated, the calculation processing device 13 may associate the time at which the roll acceleration φ was detected when storing the roll acceleration φ in memory 13b. If there is no roll acceleration φ obtained exactly time t before the time point at which the corrected vertical accelerations αzrla and αzrra are calculated, the value of roll acceleration φ obtained at the time closest to that time may be used, or the corrected vertical accelerations αzrla and αzrra may be calculated using the average value of the roll acceleration φ obtained before and after that time point.

As described above, the vibration information estimation device 1 of this embodiment calculates the delay time t from the values of the speed v and the wheelbase Lh, and calculates the correction value αφ using the roll acceleration _φ obtained at a time that is the delay time t earlier than the time when the processing by the correction unit 4 is performed. In other words, when the stroke displacement is estimated using the observer 5 from the vertical accelerations αzrl and αzrr, the roll acceleration φ detected before the delay time t described above will have an effect, so the correction unit 4 calculates the correction _value αφ using the roll acceleration φ detected before the delay time t. Meanwhile, the vertical accelerations αzrl and αzrr and the roll acceleration φ are obtained by processing the accelerations _α1 , _α2 , and _α3 obtained at the same time, as described above. If the correction value _αφ is calculated by simply multiplying the roll acceleration φ obtained simultaneously with the vertical accelerations αzrl and αzrr by Lt/2, the phase of the roll acceleration φ is delayed, making it impossible to accurately estimate the stroke displacement. Therefore, when using the roll acceleration φ obtained simultaneously with the vertical accelerations αzrl and αzrr, it is sufficient to filter the roll acceleration φ according to the velocity v of the vehicle V and adjust the phase so that it is appropriate for estimating the stroke displacement. Therefore, in the corrector 4, in addition to determining the correction value αφ using the roll acceleration _φ detected the delay time t before, the correction value αφ may be determined by using the roll acceleration φ obtained simultaneously with the vertical accelerations αzrl and _αzrr after performing processing to adjust its phase according to the velocity v. From the viewpoint of control stability, the filter processing of the roll acceleration φ may perform either phase lag compensation or phase lead compensation as appropriate.

In this way, the calculation processing device 13 functions as a correction unit 4 that performs processing to remove the influence of the roll acceleration φ from the vertical accelerations αzrl, αzrr of the rear wheels Wrl, Wrr based on the speed v of the vehicle V and the wheelbase value Lh of the vehicle V, thereby determining the corrected vertical accelerations αzrla, αzrra.

The observer 5 comprises a single-wheel model 5a that represents characteristics limited to the vertical movement of the rear wheels Wrl and Wrr relative to the vehicle body B, which is the subject of estimation; a damping coefficient map 5b that determines the damping coefficient of the shock absorber D to be input to the single-wheel model 5a; an observer gain setting unit 5c; and a differentiator 5d. The processor 13 processes each part of the observer 5, and this is implemented.

As shown in Figure 6, the single-wheel model 5a is a model that includes a sprung member U, an unsprung member W, a shock absorber D and suspension spring S interposed between the sprung member U and the unsprung member W, and a tire Ti between the unsprung member W and the road surface R. The single-wheel model 5a receives the corrected vertical acceleration αzrla (αzrra) and the observer gain G output by the observer gain setting unit 5c, and estimates and outputs the stroke displacement.

If the mass of sprung member U is Mu, the mass of unsprung member W is Mw, the spring constant of suspension spring S is Ks, the spring constant of tire Ti is Kt, the displacement of sprung member U is Xu, the displacement of unsprung member W is Xw, and the displacement of road surface R is Xr, the equation of motion for sprung member U is given by equation (1) below, and the equation of motion for unsprung member W is given by equation (2) below. Note that in equations (1) and (2), Cd(i) represents the damping coefficient of shock absorber D, and (i) indicates that the damping coefficient changes depending on the current i applied to damping force adjustment unit F.

When the state quantity estimated by the one-wheel model 5a is x, the observation quantity is y1, the output estimated by the observer 5 is y, and the corrected vertical acceleration αzrla (αzrra) is a known input u, the state equation and observation equation of the one-wheel model 5a are expressed by the following equations (3) and (4). Note that A, B, C, and D in equations (3) and (4) are coefficient matrices, and G is the observer gain described above.

Here, if the variable vector x estimated by the one-wheel model 5a in the observer 5 is defined as four state quantities, and y1, which corresponds to the output of the controlled object, and y, which corresponds to the output of the observer 5, are defined as the vertical acceleration of the vehicle body B directly above the rear wheel Wrl (Wrr), then the variable vector x can be expressed by the following equation (5). In the variable vector x in equation (5), Xw-Xr represents the displacement between the unsprung member W and the road surface R, Xu-Xw represents the stroke displacement which is the displacement between the sprung member U and the unsprung member W, the differential value of Xu represents the vertical velocity of the sprung member U, and the differential value of Xw represents the vertical velocity of the unsprung member W. In addition, in the one-wheel model 5a in the observer 5, the output is the vertical acceleration of the sprung member U, and the output of the one-wheel model 5a can be calculated by the following equation (6). The sprung member U is the vehicle body B directly above the rear wheels Wrl and Wrr, and the unsprung member W is the rear wheels Wrl and Wrr. Therefore, the displacement between the sprung member U and the unsprung member W is nothing but the vertical stroke displacement between the vehicle body B and the rear wheels Wrl (Wrr). Furthermore, the vertical acceleration output by the single-wheel model 5a is an estimated value of the vertical acceleration of the vehicle body B directly above the rear wheels Wrl and Wrr.

Therefore, the calculation processing device 13 calculates the above-mentioned equation (4) to obtain the desired stroke displacement, as well as state quantities such as the displacement between the unsprung member W and the road surface R, the vertical velocity of the sprung member U, and the vertical velocity of the unsprung member W, and also calculates equation (5) to obtain the vertical acceleration of the sprung member U. By performing calculations in this way, the calculation processing device 13 realizes the one-wheel model 5a in the observer 5, and estimates state quantities such as the stroke displacement, the displacement between the unsprung member W and the road surface R, the vertical velocity of the sprung member U, and the vertical velocity of the unsprung member W, as well as the vertical acceleration of the vehicle body B directly above the rear wheels Wrl, Wrr.

Damping coefficient map 5b contains a map showing the relationship between the stroke speed of shock absorber D, the current i supplied to damping force adjustment unit F, and the damping coefficient Cd(i). A differentiator 5d is provided upstream of damping coefficient map 5b, and the stroke speed obtained by differentiating the stroke displacement estimated by single-wheel model 5a using differentiator 5d is input to damping coefficient map 5b. Furthermore, the current i supplied to damping force adjustment unit F uses the current value specified by the command given to drive circuit 14 by control device C, and the current value specified by the command is input to damping coefficient map 5b as current i. Specifically, calculation processing unit 13 differentiates the stroke displacement estimated by single-wheel model 5a to obtain the stroke speed, and performs map calculations using the stroke speed and current i as parameters to obtain the damping coefficient Cd(i), thereby realizing damping coefficient map 5b and differentiator 5d.

The observer gain setting unit 5c includes an adder 5c1 that calculates the deviation between the vertical acceleration of the vehicle body B directly above the rear wheel Wrl (Wrr) estimated by the single-wheel model 5a and the corrected vertical acceleration αzrla (αzrra), and a gain calculation unit 5c2 that calculates the observer gain G using the deviation calculated by the adder 5c1 and the damping coefficient Cd(i) output by the damping coefficient map 5b as input and inputs the result to the single-wheel model 5a.

The gain calculation unit 5c2 calculates the observer gain G so that the deviation calculated by the adder 5c1 converges to zero. In the vibration information estimation device 1 of this embodiment, the gain calculation unit 5c2 calculates the observer gain G from the minimum and maximum values that the damping coefficient Cd(i), which is the output value of the damping coefficient map 5b, can take, and the covariance matrices Q and R. The processing of the adder 5c1 and the gain calculation unit 5c2 is realized by the calculation processing unit 13.

The observer 5 processes the corrected vertical acceleration αzrla of the left rear wheel Wrl and the corrected vertical acceleration αzrra of the right rear wheel Wrr, and the calculation processing device 13 calculates the stroke displacement between the vehicle body B and the left rear wheel Wrl and the stroke displacement between the vehicle body B and the right rear wheel Wrr at a predetermined calculation cycle.

The stroke displacement between vehicle body B and the left rear wheel Wrl and the stroke displacement between vehicle body B and the right rear wheel Wrr obtained in this way are input to the target damping force calculation unit 20 in the control device C, along with the vertical accelerations αzrl and αzrr of the rear wheels Wrl and Wrr.

In addition, in this embodiment, the control device C is equipped with a vertical acceleration detection unit 31 that detects the vertical accelerations αzfl, αzfr of the vehicle body B directly above the front wheels Wfl, Wfr in order to control the damping force of the shock absorbers D interposed between the vehicle body B and the front wheels Wfl, Wfr of the vehicle V, and a stroke displacement estimation device 30 that estimates the stroke displacement between the vehicle body B and the front wheels Wfl, Wfr. As described above, the control device C is equipped with a stroke displacement estimation device 30, as well as a target damping force calculation unit 20 that calculates target damping forces Ffl, Ffr, Frl, Frr using the stroke displacements of the rear wheels Wrl, Wrr estimated by the vibration information estimation device 1 and the stroke displacements of the front wheels Wfl, Wfr estimated by the stroke displacement estimation device 30, and a command current determination unit 21 that calculates target currents Ifl, Ifr, Irl, Irr to be supplied from the target damping forces Ffl, Ffr, Frl, Frr to the damping force adjustment units F of the dampers D of each of the four wheels Wfl, Wfr, Wrl, Wrr.

When estimating the stroke displacement between the vehicle body B and the front wheels Wfl, Wfr in the traveling direction of the vehicle V, the phase of the estimated stroke displacement does not lag even if the acceleration component due to roll acceleration is not removed. Therefore, when estimating the stroke displacement between the vehicle body B and the front wheels Wfl, Wfr located in front of the traveling direction of the vehicle V, the processing of the correction unit 4 in the configuration of the vibration information estimation device 1 is not required. Although not shown, the front wheel stroke displacement estimation device 30 has a configuration in which the roll acceleration detection unit 2 and correction unit 4 are omitted from the configuration of the vibration information estimation device 1, and the detected vertical acceleration is input to the observer 5 without correction to estimate the stroke displacement.

Therefore, in the stroke displacement estimation device 30, the vertical accelerations αzfl, αzfr of the vehicle body B directly above the front wheels Wfl, Wfr are input without correction to the single-wheel model 5a in the observer 5 to estimate the stroke displacement between the vehicle body B and the front wheels Wfl, Wfr. The vertical accelerations αzfl, αzfr of the vehicle body B directly above the front wheels Wfl, Wfr can be calculated by the calculation processing device 13 using the bounce acceleration, pitch acceleration, and roll acceleration φ calculated as described above, as well as the tread value Ltf and wheelbase value Lh of the front wheels Wfl, Wfr, and the vertical acceleration detection unit 31 is realized by the processing of this calculation processing device 13.

The stroke displacement between the vehicle body B and the front wheels Wfl, Wfr estimated in this way by the stroke displacement estimation device 30 and the vertical accelerations αzfl, αzfr of the vehicle body B directly above the front wheels Wfl, Wfr are both input to the target damping force calculation unit 20 of the control device C. In addition, the stroke displacement at the rear wheels Wrl, Wrr and the vertical accelerations αzrl, αzrr of the vehicle body B directly above the rear wheels Wrl, Wrr estimated by the vibration information estimation device 1 are input to the target damping force calculation unit 20.

The target damping force calculation unit 20 calculates target damping forces Ffl, Ffr, Frl, Frr of the shock absorbers D of the four wheels Wfl, Wfr, Wrl, Wrr (front, rear, left, and right) in order to suppress vibration of the vehicle body B by skyhook control based on Karnop's law. Specifically, the target damping force calculation unit 20 differentiates the stroke displacements at the four wheels Wfl, Wfr, Wrl, Wrr to obtain stroke velocities Szfl, Szfr, Szrl, Szrr, and calculates the required damping forces Ffl ^* , Ffr ^* , Frl ^* , Frr ^* by multiplying the vertical velocities Vzfl, Vzfr, Vzrl, Vzrr obtained by integrating the vertical accelerations αzfl, αzfr, αzrl, αzrr by the skyhook damping coefficient Cs.

The shock absorber D cannot exert a force in a direction that promotes extension during an extension operation, and cannot exert a force in a direction that promotes contraction during a contraction operation. Therefore, if the direction of the required damping forces Ffl ^* , Ffr ^* , Frl ^* , Frr ^* calculated by the target damping force calculation unit 20 is a direction in which the shock absorber D cannot exert a force, it is necessary to minimize the damping force of the shock absorber D in accordance with Karnop's law so that the damping force exerted by the shock absorber D does not vibrate the vehicle body B. For example, whether the direction of the required damping force Ffl ^* for the shock absorber D of the front wheel Wfl is a direction in which the shock absorber D cannot exert a force can be determined by the sign of the product of the stroke speed Szfl of the front wheel Wfl and the corresponding up-and-down speed Vzfl. If the direction of the upward movement of the vehicle body B is defined as positive and the stroke speed when the shock absorber D is extended is defined as positive, when both the speed of the vehicle body B and the stroke speed of the shock absorber D are positive values, the shock absorber D can exert a damping force that suppresses the rise of the vehicle body B. When both the speed of vehicle body B and the stroke speed of shock absorber D are negative values, shock absorber D is able to exert a damping force that suppresses the descent of vehicle body B. When the signs of the values of the speed of vehicle body B and the stroke speed of shock absorber D are opposite, the damping force exerted by shock absorber D promotes the ascent or descent of vehicle body B. Therefore, when the value of the product of the speed of vehicle body B and the stroke speed of shock absorber D is positive, it can be seen that the direction in which the damping force of shock absorber D for front wheel Wfl is generated coincides with the direction of the required damping force Ffl ^* . A similar determination can be made for the remaining three wheels Wfr, Wrl, and Wrr to determine whether shock absorber D can generate a damping force in a direction that coincides with the direction of the required damping forces Ffr ^* , Frl ^* , and Frr ^* .

When the target damping force calculation unit 20 determines that it is possible to generate damping forces in directions that match the directions of the required damping forces Ffl ^* , Ffr ^* , Frl ^* , Frr ^* for the shock absorbers D of each of the four wheels Wfl, Wfr, Wrl, Wrr, the required damping forces Ffl ^* , Ffr ^* , Frl ^* , Frr ^* are set to the target damping forces Ffl, Ffr, Frl, Frr, respectively.

On the other hand, if the target damping force calculation unit 20 determines that it is not possible to generate damping forces in the direction consistent with the required damping forces Ffl ^* , Ffr ^* , Frl ^* , Frr ^* for the shock absorbers D of each of the four wheels Wfl, Wfr, Wrl, and Wrr, it sets the target damping forces Ffl, Ffr, Frl, and Frr to the minimum values that the shock absorbers D can generate.

The target damping force calculation unit 20 calculates the target damping force using skyhook control, which aims to suppress vibration of the vehicle body B. However, in addition to or instead of the skyhook control, the final target damping force may be calculated based on a control law for suppressing vibration of the wheels Wfl, Wfr, Wrl, and Wrr or a control law for stabilizing the posture of the vehicle body B.

The target damping forces Ffl, Ffr, Frl, and Frr calculated by the target damping force calculation unit 20 are input to the command current determination unit 21. The command current determination unit 21 calculates the target currents Ifl, Ifr, Irl, and Irr to be supplied to the damping force adjustment unit F so that each shock absorber D for each of the four wheels Wfl, Wfr, Wrl, and Wrr exerts the damping force according to the target damping forces Ffl, Ffr, Frl, and Frr. The command current determination unit 21 has, for example, a map or function for calculating the target current using the target damping force as a parameter, and calculates the target currents Ifl, Ifr, Irl, and Irr from the target damping forces Ffl, Ffr, Frl, and Frr using the map or function. If the flow rate passing through the damping force adjustment unit F changes depending on the stroke speed of the shock absorber D, and the damping force generated by the shock absorber D changes with respect to the current, the command current determination unit 21 may determine the target currents Ifl, Ifr, Irl, and Irr using a map or function for determining current using the stroke speed and target damping force as parameters. The processing of each unit of this control device C is specifically performed by the arithmetic processing unit 13, and the control device C is realized by the processing of the arithmetic processing unit 13.

In this way, the control device C receives inputs of the vertical accelerations αzfl, αzfr, αzrl, αzrr and stroke displacement of the vehicle body B directly above the four wheels Wfl, Wfr, Wrl, Wrr of the vehicle V, calculates the target currents Ifl, Ifr, Irl, Irr, and outputs commands indicating the currents to each drive circuit 14. The commands indicating the currents are also input to the damping coefficient map 5b in the observer 5 and used in calculations to determine the damping coefficients in the damping coefficient map 5b. The drive circuit 14 then supplies the current of the value indicated by the command to the damping force adjuster F. Therefore, the suspension device Sd, which includes the shock absorber D, vibration information estimation device 1, and control device C, processes the sequentially detected vertical accelerations αzfl, αzfr, αzrl, αzrr and controls the damping force generated by the shock absorber D to suppress vibration of the vehicle body B and improve ride comfort in the vehicle V.

The configuration of each part of the vibration information estimation device 1, control device C, and shock absorber D in the suspension device Sd has been explained above. Below, the processing in the calculation processing device 13 to realize the vibration information estimation device 1 will be explained using the flowchart shown in Figure 7.

The arithmetic processing unit 13 repeatedly executes the following steps F1 to F7 at a predetermined calculation cycle. First, the arithmetic processing unit 13 calculates the vertical accelerations αzrl, αzrr and the roll acceleration φ of the vehicle body B directly above the rear wheels Wrl, Wrr from the accelerations _α1 , _α2 , _α3 detected by the acceleration sensors 10, 11, 12 (step F1). Next, the arithmetic processing unit 13 calculates a correction value _αφ based on the values of the speed v, roll acceleration φ, wheel base Lh, and tread Lt of the vehicle V (step F2).

Next, the arithmetic processing unit 13 calculates the corrected vertical accelerations αzrla and αzrra by adding or subtracting the correction value _αφ to or from the vertical accelerations αzrl and αzrr as described above (step F3).Then, the arithmetic processing unit 13 calculates the deviation between the corrected vertical accelerations αzrla and αzrra and the estimated values of the vertical accelerations calculated in the previous calculation cycle (step F4).

Furthermore, the calculation processing device 13 performs a map calculation using as parameters a command indicating the current i to be applied to the damping force adjustment unit F of the shock absorber D, which is determined by processing as the control device C, and the stroke speed obtained by differentiating the stroke displacement determined in the previous calculation cycle, to determine the damping coefficient Cd(i) (step F5).

Then, the calculation processing device 13 calculates the observer gain G from the deviation calculated in step F4 and the damping coefficient Cd(i) calculated in step F5 (step F6), sets the observer gain G of the observer 5, and performs the calculations required for processing as the observer 5 using the corrected vertical accelerations αzrla and αzrra to calculate the stroke displacement (step F7).

The calculation processing device 13 repeatedly executes the processes from steps F1 to F7 at a predetermined calculation cycle to calculate the stroke displacement from the vertical accelerations αzrl, αzrr and the roll acceleration φ. In this way, the calculation processing device 13 executes the processes from steps F1 to F7 to realize each part of the vibration information estimation device 1.

As described above, the vibration information estimation device 1 of this embodiment is configured to include a roll acceleration detection unit 2 that detects roll acceleration φ, which is the acceleration in the roll direction of the vehicle body B of a vehicle V having front, rear, left, and right wheels Wfl, Wfr, Wrl, and Wrr; a vertical acceleration detection unit 3 that detects vertical accelerations αzrl, αzrr, which are the vertical accelerations of the vehicle body B directly above the rear wheels Wrl, Wrr in the direction of travel of the vehicle V; a correction unit 4 that corrects the vertical accelerations αzrl, αzrr based on the roll acceleration φ; and an observer 5 that uses the vertical accelerations αzrla, αzrra corrected by the correction unit 4 as input and estimates the relative stroke displacement (vibration information) in the vertical direction between the vehicle body B and the rear wheels Wrl, Wrr of the vehicle V based on the state equation of a single-wheel model 5a.

The vibration information estimation device 1 configured in this manner is equipped with a correction unit 4 that corrects the vertical accelerations αzrl and αzrr based on the roll acceleration φ, making it possible to remove from the vertical accelerations αzrl and αzrr the acceleration components due to roll that interfere with the estimation of stroke displacement by the observer 5. Therefore, because the vibration information estimation device 1 can remove the acceleration components due to roll from the vertical accelerations αzrl and αzrr, the phase of the stroke displacement (vibration information) estimated by the observer 5 does not lag behind the actual stroke displacement, allowing for accurate estimation of stroke displacement (vibration information).

In addition, in the vibration information estimation device 1 of this embodiment, the correction unit 4 assumes that the rear wheels Wrl, Wrr pass over the same road surface as the front wheels Wfl, Wfr in the traveling direction of the vehicle V, and corrects the vertical accelerations αzrl, αzrr detected when the rear wheels Wrl, Wrr pass over the same road surface based on the roll acceleration φ obtained when the front wheels Wfl, Wfr pass over the same road surface. With the vibration information estimation device 1 configured in this manner, when the front wheels Wfr, Wfr and the rear wheels Wrl, Wrr pass over the same road surface, the vertical accelerations αzrl, αzrr can be corrected using the roll angular velocity φ obtained when the front wheels Wfr, Wfr travel on the same road surface, allowing for more accurate estimation of stroke displacement (vibration information).

Furthermore, the suspension device Sd of this embodiment includes a shock absorber D with adjustable damping force interposed between the vehicle body B and the rear wheels Wrl, Wrr, a control device C that controls the shock absorber D, and a vibration information estimation device 1. The control device C controls the shock absorber D based on the stroke displacement (vibration information) estimated by the vibration information estimation device 1. With the suspension device Sd configured in this manner, the shock absorber D is controlled based on the accurately estimated stroke displacement (vibration information), thereby effectively suppressing vibration of the vehicle body B and improving ride comfort in the vehicle. Note that while the suspension device Sd of this embodiment includes a shock absorber D and controls the shock absorber D using the control device C, it may also be possible to include an actuator that can adjust the generated thrust instead of the shock absorber D and control the actuator using the control device C. Even in this case, the suspension device Sd can control the actuator based on the accurately estimated stroke displacement (vibration information), thereby effectively suppressing vibration of the vehicle body B and improving ride comfort in the vehicle. When controlling an actuator, a map or function for determining the thrust generated by the actuator can be provided instead of the damping coefficient map 5b in the vibration information estimation device 1.

In addition, while the vibration information described above is stroke displacement, the vibration information estimated by the observer 5 may also be stroke speed or stroke acceleration. Furthermore, in addition to stroke displacement and stroke speed, the observer 5 may also estimate the vertical speed and displacement of the vehicle body B, and the acceleration, speed and displacement of the wheels Wfr, Wfr, Wrl, and Wrr. The vibration information selected may be determined according to the state quantity used in the control of the suspension device Sd.

In the suspension device Sd of this embodiment, the stroke displacement of the front wheels Wfl, Wfr is estimated by the stroke displacement estimation unit 30 without processing by the correction unit 4. However, the vibration information estimation device 1 may be configured to process the stroke displacement (vibration information) of both the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr of the vehicle V, and depending on the direction of travel of the vehicle V, the stroke displacement (vibration information) of the wheels on the front side in the direction of travel may be estimated without processing by the correction unit 4, and the stroke displacement (vibration information) of the wheels on the rear side in the direction of travel may be estimated by processing by the correction unit 4.

Furthermore, in the suspension device Sd of this embodiment, each part of the vibration information estimation device 1 and the control device C is realized by processing by the arithmetic processing device 13, but the vibration information estimation device 1 and the control device C may be separate and independent hardware, or each part of the vibration information estimation device 1 and the control device C may be configured by different hardware.

While the preferred embodiments of the present invention have been described in detail above, modifications, variations, and variations are possible without departing from the scope of the claims.

1... Vibration information estimation device, 2... Roll acceleration detection unit, 3... Vertical acceleration detection unit, 4... Correction unit, 5... Observer, 5a... Single-wheel model
B: vehicle body, C: control device, D: shock absorber, Sd: suspension device, V: vehicle, Wfl, Wfr: front wheels, Wrl, Wrr: rear wheels,

Claims (3)

a roll acceleration detection unit that detects roll acceleration, which is acceleration in the roll direction of a vehicle body of a vehicle having wheels on the front, rear, left, and right sides;
a vertical acceleration detection unit that detects vertical acceleration, which is acceleration of the vehicle body in the vertical direction directly above the rear wheels in the traveling direction of the vehicle;
a correction unit that corrects the vertical acceleration based on the roll acceleration of a front wheel in a traveling direction of the vehicle ;
an observer that receives the vertical acceleration corrected by the correction unit as an input and estimates relative vertical vibration information between the body and the rear wheels of the vehicle based on a state equation of a one-wheel model. The vibration information estimation device according to claim 1, characterized in that the correction unit corrects the vertical acceleration detected when the rear wheels pass over the same road surface as the front wheels in the direction of travel of the vehicle, based on the roll acceleration obtained when the front wheels pass over the same road surface, assuming that the rear wheels pass over the same road surface as the front wheels in the direction of travel of the vehicle. a shock absorber with adjustable damping force or an actuator with adjustable thrust force interposed between the vehicle body and the rear wheel;
a control device for controlling the shock absorber or the actuator;
The vibration information estimation device according to claim 1 or 2,
The suspension device is characterized in that the control device controls the shock absorber or the actuator based on the vibration information estimated by the vibration information estimation device.