Suspension control system

Abstract

The present invention provides a suspension control device that can improve ride comfort in a vehicle without requiring the installation of sensors on the unsprung mass. [Solution] The suspension control device 1 includes a sprung speed detection unit 2 that detects the vertical sprung speed of the sprung member B, a control unit 4 that controls an actuator (suspension device) A, which is capable of generating a control force to suppress vibration of the sprung member B and is either in parallel with a passive shock absorber or has a damping element, based on the sprung speed, and a signal processing unit 3 that processes the sprung speed signal and widens the frequency band in which the gain of the sprung speed signal after processing is greater than or equal to a predetermined reference value in the frequency characteristics of the gain from the signal input to the control unit 4 to the sprung speed, compared to the frequency band in which the gain of the sprung speed signal before processing is greater than or equal to a predetermined reference value, and the control unit 4 controls the actuator (suspension device) A based on the processed sprung speed signal.

Description

Technical Field

[0001] The present invention relates to a suspension control device.

Background Art

[0002] Conventionally, as a suspension control device that controls an actuator interposed between an upper spring member and a lower spring member in a vehicle, in order to suppress vibrations of the vehicle body (upper spring member) and the wheels (lower spring member) that occur when the wheels cross road surface irregularities during driving, a target thrust is obtained and the target thrust is output to the actuator.

[0003] Specifically, the suspension control device obtains a target thrust by adding a first vibration suppression force for suppressing upper spring vibrations obtained from the upper spring speed, which is the vertical speed of the vehicle body, and a second vibration suppression force for suppressing lower spring vibrations obtained from the lower spring speed, which is the vertical speed of the wheels (see, for example, Patent Document 1).

[0004] Such a suspension control device is excellent in that it can suppress vibrations of the wheels in addition to suppressing vibrations of the vehicle body, and thus can achieve a good ride comfort in a vehicle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventional suspension control systems need to detect not only the vertical velocity of the sprung mass but also the vertical velocity of the unsprung mass. In the case of automobiles, four acceleration sensors are required to detect the vertical velocity of all four wheels. Thus, while conventional suspension control systems can achieve a good ride, they have the problem of requiring sensors to be installed on the wheels.

[0007] To address this problem, one approach is to control the actuator by feeding back only the acceleration of the sprung mass, and to place a passive shock absorber in parallel with the actuator that generates damping force during expansion and contraction to suppress vibrations of both the sprung mass and unsprung mass. However, in this case, the actuator cannot dampen the vibrations of the unsprung mass, and the vibration of the unsprung mass is only damped by the damping force of the shock absorber. Therefore, in terms of ride comfort, this would be inferior to conventional suspension control systems that feed back the accelerations of both the sprung mass and unsprung mass to control the actuator.

[0008] Therefore, the object of the present invention is to provide a suspension control device that can improve ride comfort in a vehicle without installing sensors on the unsprung member. [Means for solving the problem]

[0009] To achieve the above objective, the suspension control device in the problem-solving means of the present invention includes: a sprung speed detection unit that detects the vertical sprung speed of a sprung member in a vehicle; a control unit that controls a suspension device, which is interposed in parallel with a passive shock absorber between the sprung member and the unsprung member in a vehicle and capable of generating a control force to suppress vibration of the sprung member, based on the sprung speed; a signal processing unit that processes the sprung speed signal and, in the frequency characteristics of the gain from the signal input to the control unit to the sprung speed output by the sprung speed detection unit, widens the frequency band in which the gain of the sprung speed signal after processing exceeds a predetermined reference value, including the sprung resonance frequency, compared to the frequency band in which the gain of the sprung speed signal before processing exceeds a predetermined reference value; and the control unit controls the suspension device based on the processed sprung speed signal.

[0010] Furthermore, the suspension control device in another solution to the problem of the present invention includes: a sprung speed detection unit that detects the vertical sprung speed of a sprung member in a vehicle; a control unit that controls a suspension device interposed between a sprung member and an unsprung member in a vehicle, capable of generating a control force to suppress vibration of the sprung member and having a damping element, based on the sprung speed; and a signal processing unit that processes the sprung speed signal and, in the frequency characteristics of the gain from the signal input to the control unit to the sprung speed output by the sprung speed detection unit, widens the frequency band in which the gain of the sprung speed signal after processing exceeds a predetermined reference value, including the sprung resonance frequency, compared to the frequency band in which the gain of the sprung speed signal before processing exceeds a predetermined reference value, and the control unit controls the suspension device based on the processed sprung speed signal.

[0011] With a suspension control device configured in this way, even though only the sprung speed is used, the vibration of the unsprung member is suppressed by a shock absorber or damping element, while the frequency band of the sprung speed signal that can suppress the vibration of the sprung member can be broadened. Therefore, vibration damping effects can be obtained not only for vibrations in the sprung resonance frequency band, but also for vibration components that are shifted from the sprung resonance frequency band to the unsprung resonance frequency band by the suspension device.

[0012] From the above, it can be concluded that, by widening the frequency band of vibrations that can be damped, the suspension control device can achieve the same vibration damping effect as a conventional suspension control device that uses both sprung speed and unsprung speed, even when using only the sprung speed signal and not the unsprung speed.

[0013] Furthermore, the signal processing unit in the suspension control device may set the reference value to 0 dB and widen the frequency band in which the gain of the processed sprung speed signal is 0 dB or higher than the frequency band in which the gain of the unprocessed sprung speed signal is 0 dB or higher. With a suspension control device configured in this way, the frequency band in which vibration of the sprung member can be suppressed can be maximized, and a vibration suppression effect on the sprung member can be obtained for vibrations across a wide frequency band.

[0014] Furthermore, the signal processing unit in the suspension control device may keep the lower limit of the frequency band where the gain of the processed sprung speed signal is 0 dB or higher unchanged, and move the upper limit closer to the unsprung resonance frequency band than the upper limit of the frequency band where the gain of the unsprung speed signal before processing is 0 dB or higher. With a suspension control device configured in this way, vibration damping effects can be obtained not only for vibrations in the sprung resonance frequency band, but also for vibrations that are close in frequency to the unsprung resonance frequency band beyond the sprung resonance frequency band, while avoiding the generation of unnecessary control forces in the suspension device for vibrations in the frequency band lower than the sprung resonance frequency band, thereby affecting the ride comfort of the vehicle when driving on good roads.

[0015] Furthermore, the signal processing unit in the suspension control device may adjust the upper limit of the frequency band at which the gain of the processed sprung speed signal is 0 dB or higher to 5 Hz, bringing it closer to the unsprung resonance frequency band. With a suspension control device configured in this way, vibration damping effects can be obtained not only for vibrations in the sprung resonance frequency band, but also for vibrations that are close in frequency to the unsprung resonance frequency band beyond the sprung resonance frequency band, while at the same time, the suspension device does not generate unnecessary control forces for vibrations in the frequency band lower than the sprung resonance frequency band, thus maintaining a good ride comfort when driving on good roads.

[0016] Furthermore, the signal processing unit in the suspension control device may be configured to include one or more filters that filter out the sprung speed signal before processing.

[0017] Furthermore, the signal processing unit in the suspension control device may include a first filter that filters the sprung speed signal before processing, a second filter that filters the sprung speed signal processed by the first filter, and an adder that adds the sprung speed signal before processing and the sprung speed signals filtered by the first and second filters. With a suspension control device configured in this way, the sprung speed signal after processing is generated by adding the sprung speed signal before processing and the sprung speed signals filtered by the first and second filters. Therefore, the frequency characteristics of the sprung speed signal after processing can be tuned by designing the first and second filters individually, and the signal processing unit can be easily designed. [Effects of the Invention]

[0018] Based on the above, the suspension control device of the present invention can improve ride comfort in a vehicle without installing sensors on the unsprung mass. [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram showing the configuration of a suspension device in one embodiment. [Figure 2] This figure shows the frequency characteristics of the gain of the sprung speed signal output by the sprung speed detection unit in response to the input to the control unit. [Figure 3] This is a Bode plot showing the frequency characteristics of the gain of the first filter in the signal processing unit. [Figure 4] This is a Bode plot showing the frequency characteristics of the gain of the second filter in the signal processing unit. [Figure 5] This figure shows the frequency characteristics of the gain of the signal representing the spring velocity after processing. [Figure 6] This figure shows the frequency characteristics of the gain from road surface input to sprung displacement when a suspension control device of one embodiment controls the suspension device. [Figure 7]This is a diagram showing the frequency characteristics of the gain of the tire deflection from the road surface input when the suspension control device of an embodiment controls the suspension device.

Embodiment for Carrying out the Invention

[0020] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. As shown in FIG. 1, a suspension control device 1 in an embodiment includes a sprung speed detection unit 2 that detects the sprung speed in the vertical direction of a sprung member B in a vehicle, a signal processing unit 3 that processes the signal of the sprung speed output by the sprung speed detection unit 2, and a control unit 4 that controls an actuator A as a suspension device interposed between the sprung member B and the unsprung member W in the vehicle and capable of generating a control force to suppress the vibration of the sprung member B.

[0021] The actuator A as a suspension device is interposed between the sprung member B and the unsprung member W in parallel with the suspension spring SP and the passive shock absorber D, and is, for example, a telescopic cylinder using hydraulic pressure or pneumatic pressure, an electric linear actuator, or the like. Although only one actuator A is shown in FIG. 1, if the vehicle V is a four-wheel vehicle, it is provided at four locations between each unsprung member W and the sprung member B. When the actuator A is driven by hydraulic pressure, although not shown, for example, it includes a pump, a pressure control valve, a switching valve, and a driver for driving these, and is driven to expand and contract by a control command input from the suspension control device 1 to the driver.

[0022] Therefore, when the actuator A receives a control command from the suspension control device 1, it expands and contracts while exerting a control force in the direction and magnitude indicated by the control command to suppress the vibration of the sprung member B and the unsprung member W. Note that the spring described between the unsprung member W and the road surface in FIG. 1 indicates the spring element of the tire T.

[0023] The shock absorber D, although not shown in the figures, comprises, for example, a cylinder, a piston inserted axially movably into the cylinder and dividing the inside of the cylinder into an extension chamber and a compression chamber, and a piston rod inserted axially movably into the cylinder and connected to the piston. When the vehicle V is traveling, the shock absorber D expands and contracts to generate a damping force when the sprung mass B and unsprung mass W move relative to each other in the vertical direction due to vibration input from the road surface, thereby suppressing vibrations of the sprung mass B and unsprung mass W.

[0024] Furthermore, the shock absorber D may be omitted if the actuator A is equipped with a damping element that dampens the relative vertical movement between the sprung member B and the unsprung member W by friction or the like, in addition to the control force generated by the control command. For example, in the case of a hydraulic actuator comprising a cylinder, a piston inserted into the cylinder so as to be movable in the axial direction and dividing the inside of the cylinder into two working chambers, a piston rod inserted into the cylinder so as to be movable in the axial direction and connected to the piston, and a pump capable of supplying pressurized oil to one of the working chambers, the actuator A only needs to be able to suppress the relative movement between the sprung member B and the unsprung member W by using one or both of the frictional force generated between the cylinder and the piston and the frictional force generated between the piston rod and the rod guide that closes the end of the cylinder and slides against the outer circumference of the piston rod as damping elements. In addition, the actuator A may be equipped with a friction member that suppresses the relative movement between the piston rod and the cylinder as a damping element, or, in the case of an actuator using an electric motor, a friction member that suppresses the movement of the movable part of the actuator A may be equipped with a friction member that suppresses the movement of the movable part of the actuator A as a damping element.

[0025] As described above, the suspension control device 1 comprises a sprung speed detection unit 2, a signal processing unit 3, and a control unit 4. In this embodiment, the sprung speed detection unit 2 is The system includes an inertial measuring device 21 that detects the angular velocity of the sprung mass B as a vehicle body around three axes: longitudinal, lateral, and vertical, that is, the three angular velocities of the sprung mass B in the roll, pitch, and yaw directions, as well as the acceleration of the sprung mass B in the longitudinal, lateral, and vertical directions, and a velocity calculation unit 22 that processes the information of the three angular velocities and three accelerations to determine the sprung mass velocity, which is the vertical velocity of the sprung mass B directly above the four unsprung mass W in the vehicle.

[0026] Specifically, the velocity calculation unit 22 determines the sprung velocity of the sprung member B directly above the four unsprung members W from the three angular velocities and three accelerations detected by the inertial measuring device 21 at the installation position for the sprung member B. The velocity calculation unit 22 determines a rotation matrix to obtain the three angular velocities and three accelerations at the center of gravity of the sprung member B by correcting the three angular velocities and accelerations detected by the inertial measuring device 21 through calibration in advance, because the detection axes for detecting the three-axis acceleration of the inertial measuring device 21 may not perfectly coincide with the front-to-back, left-to-right, and up-and-down directions of the sprung member B, and the inertial measuring device 21 may not be installed on the sprung member B at the center of gravity of the sprung member B. Then, the velocity calculation unit 22 uses the rotation matrix to correct the three angular velocities and accelerations detected by the inertial measuring device 21 to obtain the three angular velocities and three accelerations at the center of gravity of the sprung member B. Once the velocity calculation unit 22 obtains the three angular velocities and three accelerations at the center of gravity of the sprung member B in this manner, it calculates the vertical velocities of the sprung member B at four points directly above the four unsprung members W based on geometric information such as the tread width of the vehicle and the distance from the vehicle's four unsprung members W to the center of gravity of the sprung member B. In this way, the sprung velocity detection unit 2 detects the vertical velocities of the sprung member B at four points directly above the four unsprung members W at a predetermined sampling period and inputs the signals of the four sprung velocities to the signal processing unit 3.

[0027] Specifically, if Ltf is the front tread width of the vehicle, Ltr is the rear tread width, Lwf is the horizontal distance between the center of gravity of the sprung member B and the front axle, Lwr is the distance between the vehicle's center of gravity and the rear axle, Zcg is the vertical displacement of the center of gravity of the sprung member B, Zsfl is the vertical displacement of the front left side of the sprung member B, Zsfr is the vertical displacement of the front right side of the sprung member B, Zsrl is the vertical displacement of the rear left side of the sprung member B, and Zsfr is the vertical displacement of the rear right side of the sprung member B, then the velocity calculation unit 22 performs calculations using the formulas shown in Equation 1 below to determine the vertical velocities of the sprung member B at four points directly above the four unsprung members. Note that the dot symbol above a variable indicates the derivative of that variable.

[0028]

number

[0029] The signal processing unit 3 performs a process to broaden the frequency band in the frequency characteristics of the gain from the signal input to the control unit 4 to the sprung speed output by the sprung speed detection unit 2, so that the gain of the processed sprung speed signal exceeds a predetermined reference value, including the sprung resonance frequency. The signal processing unit 3 performs the same process on the four sprung speed signals and inputs the four processed sprung speed signals corresponding to the sprung member B directly above the unsprung member W to the control unit 4.

[0030] Specifically, in the suspension control device 1 of this embodiment, the signal processing unit 3 includes a first pass 32 that inputs the sprung speed signal directly to an adder 31 which acts as an adder; a second pass 33 that inputs the sprung speed signal filtered by the first filter 34 to the adder 31, and a third pass 35 that inputs the sprung speed signal filtered by the first filter 34 and the second filter 36 to the adder 31, and a second filter 36 that filters the sprung speed signal filtered by the first filter 34.

[0031] The sprung mass velocity signal, which passes through the first pass 32 and is input to the summing unit 31, has a frequency characteristic in which the gain peaks above a predetermined reference value of 0 dB around 1 Hz, the sprung mass resonance frequency band, because the sprung mass resonance frequency is around 1 Hz, as shown in Figure 2. Figure 2 shows the frequency characteristic of the gain from the signal input to the control unit 4 (described later) to the sprung mass velocity output by the sprung mass velocity detection unit 2. The control unit 4 generates and outputs control signals to be given to each actuator A in response to the input of the sprung mass velocity signal. Therefore, the frequency characteristic of the gain shown in Figure 2 shows the frequency characteristic of the gain of the sprung mass velocity signal output by the sprung mass velocity detection unit 2 as a result of the actuator A being driven by the control signal generated by the control unit 4 after the signal is input to the control unit 4. When the sprung mass velocity signal output by the sprung mass velocity detection unit 2 is fed back to the control unit 4, vibrations of the sprung mass member B in the frequency band above 0 dB are suppressed.

[0032] As shown in Figure 3, the first filter 34 has a characteristic where the gain exceeds 0 dB around 1 Hz, which is the sprung resonance frequency band, and peaks at a higher value around 4 Hz. As shown in Figure 4, the second filter 36 has a characteristic where the gain exceeds 0 dB around 1 Hz, which is the sprung resonance frequency band, and the gain peaks around 3-4 Hz, but the peak gain is smaller than that of the first filter 34. When the sprung velocity signal filtered by the first filter 34 is filtered, the output signal has a slightly higher gain around 1 Hz, which is the sprung resonance frequency band, while the gain around 3-4 Hz is higher than the gain around 1 Hz.

[0033] The summing unit 31 adds the sprung velocity signal detected by the sprung velocity detection unit 2, which is input from the first pass 32, the filtered sprung velocity signal filtered by the first filter 34 with a large gain around 4 Hz, and the filtered sprung velocity signal filtered by the first filter 34 and the second filter 36 with a large gain around 3-4 Hz, and outputs the result. The output of the summing unit 31 is the processed sprung velocity signal after all processing has been completed by the signal processing unit 3. As shown in Figure 5, the frequency characteristics of the processed sprung velocity vibration show that the gain around 1 Hz, which is the sprung resonance frequency band, exceeds 0 dB and is at its maximum, and the gain up to around 3 Hz also exceeds 0 dB.

[0034] Comparing the frequency characteristics of the gain of the sprung speed signal detected by the sprung speed detection unit 2, which is the sprung speed signal before processing shown in Figure 2, with the frequency characteristics of the gain of the sprung speed signal after processing shown in Figure 5, the processed sprung speed signal has characteristics in which the gain is greater than that of the unprocessed sprung speed signal, not only in the sprung resonance frequency band around 1 Hz but also up to around 3 Hz, exceeding 0 dB.

[0035] Therefore, in the suspension control device 1 of this embodiment, by detecting and processing only the sprung speed signal, the bandwidth exceeding 0 dB in the frequency characteristics of the processed sprung speed signal used for control can be broadened toward the frequency band around 10 Hz, which is the resonant frequency band of the unsprung member. When the frequency band exceeding 0 dB of the processed sprung speed signal is broadened in this way, the control unit 4 can determine the target control force to be output to actuator A from the processed sprung speed signal, thereby enabling not only suppression of vibrations in the resonant frequency band of the sprung member B, but also suppression of vibrations in frequency bands exceeding the sprung resonance frequency band. The predetermined reference value is a threshold value for the gain used to define the frequency band in which vibration of the sprung member B can be suppressed. Since vibration of the sprung member B can be suppressed in any frequency band where the gain of the processed sprung speed signal is 0 dB or higher, it can be set to any value greater than or equal to 0 dB with 0 dB as the lower limit. Furthermore, the signal processing unit 3 should be designed according to the frequency characteristics of the gain from the signal input to the control unit 4 to the signal of the sprung speed.

[0036] Next, the control unit 4 performs the same processing on the four processed sprung velocity signals to generate and output control signals to be given to each actuator A connected to the four unsprung members W. Specifically, the control unit 4 multiplies each of the four processed sprung velocity signals processed by the signal processing unit 3 by a control gain to determine the target control force value that the actuator A corresponding to each part of the four unsprung members W should output. The control unit 4 does not perform any processing to modify or correct the sprung velocity signals, but generates control signals according to the control law used by the control unit 4 for the sprung velocity signals processed by the signal processing unit 3. Therefore, for example, when the control unit 4 performs skyhook control, the control unit 4 uses a predetermined damping coefficient of the skyhook damper as the control gain and multiplies the sprung velocity signal processed by the signal processing unit 3 by the control gain to determine the target control force. The sign of the target control force value indicates the direction of the control force that the actuator A should output, and the value indicates the magnitude of the control force. The control unit 4 outputs a control command to the driver in actuator A, specifying the magnitude and direction of the control force to be output by actuator A, in order to cause actuator A to output the determined target control force.

[0037] When actuator A receives a control command from control unit 4, it drives according to the control command to apply a control force to the sprung member B, thereby suppressing vibration of the sprung member B.

[0038] The suspension control device 1 configured in this way is housed, for example, in an out-of-disc housing that also houses the sprung speed detection unit 2, the signal processing unit 3, and the control unit 4, and is installed on the sprung member B. The sprung speed detection unit 2 may be installed on the sprung member B separately from the signal processing unit 3 and the control unit 4, and the driver for the actuator A may be installed in the out-of-disc housing that houses the suspension control device 1, separately from the actuator body which is interposed between the sprung member B and the unsprung member of the actuator A.

[0039] The suspension control device 1, as a hardware resource, may specifically include, although not shown in the diagram, an interface for receiving signals output by the inertial measuring device 21 in the sprung speed detection unit 2, a storage device such as a ROM (Read Only Memory) for storing programs used in the velocity calculation unit 22, signal processing unit 3, and control unit 4, a computing device such as a CPU (Central Processing Unit) for executing processing based on the programs, and a storage device such as a RAM (Random Access Memory) for providing memory space to the CPU. The velocity calculation unit 22, signal processing unit 3, and control unit 4 can be realized by the execution of the programs by the CPU. Alternatively, the velocity calculation unit 22, signal processing unit 3, and control unit 4 may be realized by analog electronic circuits instead of by the execution of the programs by the CPU.

[0040] The suspension control device 1 is configured as described above and operates as follows: The sprung speed detection unit 2 detects the sprung speed at a predetermined sampling period and inputs it to the signal processing unit 3. The signal processing unit 3 processes the sprung speed signal detected by the sprung speed detection unit 2 and, in the frequency characteristics of the gain from the signal input to the control unit 4 to the sprung speed output by the sprung speed detection unit 2, it does not change the lower limit of the frequency band exceeding 0 dB in the frequency characteristics of the processed sprung speed signal, but expands the upper limit toward a frequency band of about 10 Hz, which is the resonant frequency of the unsprung member. In the suspension control device 1 of this embodiment, the frequency band in which the processed sprung speed signal exceeds 0 dB is expanded not only around 1 Hz but also from 1 Hz to around 4 Hz.

[0041] The control unit 4 uses the processed sprung mass velocity signal, which extends the frequency band above 0 dB not only around 1 Hz but also from 1 Hz to around 4 Hz, to determine the target control force. If the sprung mass velocity signal detected by the sprung mass velocity detection unit 2 is used directly for control of the control unit 4, it is possible to determine the target control force that will cause actuator A to output a control force to suppress vibrations in the frequency band around 1 Hz of the sprung mass resonance frequency band. However, it is difficult to obtain a target control force that will provide sufficient damping effect for vibration components shifted from the sprung mass resonance frequency band to the unsprung mass resonance frequency band. In contrast, the suspension control device 1 of this embodiment determines the target control force using the processed sprung mass velocity signal, which extends the frequency band above 0 dB not only around 1 Hz but also from 1 Hz to around 4 Hz. Therefore, it is possible to determine a target control force that will provide damping effect not only for vibrations in the sprung mass resonance frequency band but also for vibration components shifted from the sprung mass resonance frequency band to the unsprung mass resonance frequency band. As for vibrations in the unsprung mass resonance frequency band, a passive shock absorber D is connected in parallel with actuator A as a suspension device, so vibrations in the unsprung mass resonance frequency band are sufficiently damped. As mentioned above, if a passive shock absorber D is not connected in parallel to actuator A, it is sufficient for actuator A itself to have a damping element that suppresses vibrations of the sprung member B, generated by friction or the like, in addition to the control commands output by the control command.

[0042] When actuator A is controlled by the suspension control device 1 of this embodiment, the frequency characteristics of the gain from road surface displacement to sprung displacement, as shown by the solid line in Figure 6, are almost the same in the sprung resonance frequency band around 1 Hz and the unsprung resonance frequency band around 10 Hz, even when compared with the frequency characteristics of the gain from road surface displacement to sprung displacement (dashed line in Figure 6) when a conventional suspension control device controls the actuator by processing signals for both sprung velocity and the vertical velocity of the unsprung member to determine the target control force. Furthermore, when actuator A is controlled by the suspension control device 1 of this embodiment, the frequency characteristics of the gain from road surface displacement to tire deflection, as shown by the solid line in Figure 7, are almost the same in the sprung resonance frequency band around 1 Hz and the unsprung resonance frequency band around 10 Hz, even when compared with the frequency characteristics of the gain from road surface displacement to tire deflection (dashed line in Figure 7) when a conventional suspension control device controls the actuator by processing signals for both sprung velocity and the vertical velocity of the unsprung member to determine the target control force.

[0043] Thus, it can be understood that the suspension control device 1 of this embodiment, which uses only the sprung speed signal and not the unsprung speed, can achieve a vibration damping effect almost equivalent to that of a conventional suspension control device that uses both the sprung speed and the unsprung speed.

[0044] As described above, the suspension control device 1 of this embodiment includes a sprung speed detection unit 2 that detects the vertical sprung speed of the sprung member B in the vehicle, a control unit 4 that controls an actuator (suspension device) A, which is interposed in parallel with a passive shock absorber or has a damping element between the sprung member B and the unsprung member W in the vehicle V, based on the sprung speed, and processes the sprung speed signal, and in the frequency characteristics of the gain from the signal input to the control unit 4 to the sprung speed output by the sprung speed detection unit 2, widens the frequency band in which the gain of the sprung speed signal after processing exceeds a predetermined reference value, including the sprung resonance frequency, compared to the frequency band in which the gain of the sprung speed signal before processing exceeds a predetermined reference value, and the control unit 4 controls the actuator (suspension device) A based on the processed sprung speed signal.

[0045] With the suspension control device 1 configured in this way, even though it only utilizes the sprung speed, it is possible to broaden the frequency band of the sprung speed signal that suppresses vibrations of the sprung member B while suppressing vibrations of the sprung member B by the shock absorber D or damping element. Therefore, vibration damping effects can be obtained not only for vibrations in the sprung resonance frequency band, but also for vibration components that have shifted from the sprung resonance frequency band to the unsprung resonance frequency band by the actuator (suspension device) A.

[0046] From the above, the suspension control device 1 of this embodiment widens the frequency band of vibrations that can be damped, so even if only the sprung speed signal is used and no unsprung speed is used, the same vibration damping effect as a conventional suspension control device that uses both sprung speed and unsprung speed can be obtained.Therefore, the suspension control device 1 of this embodiment not only provides a good ride comfort in the vehicle, similar to a conventional suspension control device, but also only requires the detection of the vertical speed of the sprung member B, eliminating the need to install a sensor to detect the vertical speed on the unsprung member W.

[0047] Furthermore, the signal processing unit 3 in the suspension control device 1 of this embodiment sets the reference value to 0 dB and widens the frequency band in which the gain of the processed sprung speed signal is 0 dB or higher than the frequency band in which the gain of the unprocessed sprung speed signal is 0 dB or higher. With the suspension control device 1 configured in this way, the vibration of the sprung member B can be suppressed because the lower limit of the gain in the frequency characteristics of the processed sprung speed signal becomes 0 dB. This maximizes the frequency band in which the vibration of the sprung member B can be suppressed, and a vibration suppression effect of the sprung member B can be obtained for vibrations across a wide frequency band.

[0048] Furthermore, in the suspension control device 1 of this embodiment, the signal processing unit 3 does not change the lower limit of the frequency band in which the gain of the processed sprung speed signal is 0 dB or more, but brings the upper limit closer to the unsprung resonance frequency band than the upper limit of the frequency band in which the gain of the unsprung speed signal before processing is 0 dB or more.

[0049] With the suspension control device 1 configured in this way, vibration damping effects can be obtained not only for vibrations in the sprung mass resonance frequency band, but also for vibrations that are beyond the sprung mass resonance frequency band and close in frequency to the unsprung mass resonance frequency band. At the same time, vibrations in the frequency band lower than the sprung mass resonance frequency band do not generate unnecessary control force in the actuator (suspension device) A, thus avoiding affecting the ride comfort of the vehicle when driving on good roads.

[0050] Furthermore, the signal processing unit 3 does not change the lower limit of the frequency band in which the gain of the processed sprung speed signal is 0 dB or higher, thereby avoiding any impact on ride comfort on good roads. However, even if the upper limit is increased while the lower limit is also decreased, vibration damping effects can still be obtained for vibrations with frequencies close to the unsprung resonance frequency band without detecting the unsprung speed. Therefore, the benefits of improved ride comfort in the vehicle and the elimination of the need to install sensors on the unsprung member W are not lost.

[0051] Furthermore, as explained above, it is preferable to bring the upper limit of the frequency band in which the gain of the processed sprung mass velocity signal exceeds 0 dB closer to the unsprung mass resonance frequency band. However, if the upper limit is brought closer to the unsprung mass resonance frequency band beyond 5 Hz, the overall gain of the processed sprung mass velocity signal will increase, causing the gain in frequency bands lower than the sprung mass resonance frequency band to significantly exceed 0 dB, which may worsen the ride comfort of the vehicle when driving on good roads. Therefore, the signal processing unit 3 in the suspension control device 1 of this embodiment sets the upper limit of the frequency band in which the gain of the processed sprung mass velocity signal is 0 dB or higher to 5 Hz, bringing it closer to the unsprung mass resonance frequency band. With the suspension control device 1 configured in this way, vibration damping effects can be obtained not only for vibrations in the sprung mass resonance frequency band, but also for vibrations that are close in frequency to the unsprung mass resonance frequency band beyond the sprung mass resonance frequency band, while at the same time, unnecessary control force is not generated in the actuator (suspension device) A for vibrations in frequency bands lower than the sprung mass resonance frequency band, thus maintaining good ride comfort of the vehicle when driving on good roads.

[0052] In this embodiment, the signal processing unit 3 in the suspension control device 1 includes a first filter 34 that filters the sprung speed signal before processing, a second filter 36 that filters the sprung speed signal filtered by the first filter 34, and an adder 31 that adds the sprung speed signal before processing and the sprung speed signal filtered by the first filter 34 and the second filter 36. With the suspension control device 1 configured in this way, the sprung speed signal after processing is generated by adding the sprung speed signal before processing and the sprung speed signal filtered by the first filter 34 and the second filter 36. Therefore, each filter can be designed individually to tune the frequency characteristics of the sprung speed signal after processing, and the signal processing unit 3 can be easily designed. Furthermore, since the sprung velocity signal filtered by the first filter 34 is filtered by the second filter 36 and added, it becomes easier to adjust the frequency band and gain that exceed the reference value in the frequency characteristics of the sprung velocity signal, and it also becomes easier to set the lower and upper limits of the frequency band that exceeds the reference value of the processed sprung velocity signal.

[0053] Incidentally, as described above, the filter in the signal processing unit 3 is composed of the first filter 34 and the second filter 36, but it may be composed of three or more filters. Further, the signal processing unit 3 includes a plurality of filters installed in parallel, and the signals of the sprung mass speeds filtered by each filter may be added.

[0054] Also, the path for processing the signal of the sprung mass speed is composed of the first path 32, the second path 33 including the first filter 34, and the third path 35 including the second filter 36. However, when these paths can be expressed by a single transfer function, the signal processing unit 3 may be configured to include only one path including one filter expressed by the transfer function. Therefore, the signal processing unit 3 may be configured to include at least one or more filters for filtering the signal of the sprung mass speed before processing.

[0055] Moreover, the signal processing unit 3 processes the signal of the sprung mass speed output by the sprung mass speed detection unit 2, and the frequency characteristic of the gain of the signal of the sprung mass speed after processing is such that the frequency band including the sprung resonance frequency and exceeding the reference value is wider than the frequency band including the sprung resonance frequency and exceeding the reference value of the frequency characteristic of the gain of the signal of the sprung mass speed before processing. Therefore, the processing of the signal processing unit 3 can be arbitrarily designed and changed within that limit. Thus, the frequency characteristics of the gains of the first filter 34 and the second filter 36 may be set to have characteristics other than the characteristics shown in FIGS. 3 and 4.

[0056] Furthermore, as described above, the suspension device interposed between the sprung member B and the unsprung member W is the actuator A, but the suspension device that is the control target of the suspension control device 1 may be a shock absorber capable of adjusting the damping force.

[0057] As described above, the preferred embodiments of the present invention have been described in detail, but modifications, deformations, and changes are possible without departing from the scope of the claims.

Explanation of Reference Numerals

[0058] 1...Suspension control device, 2...Sprung speed detection unit, 3...Signal processing unit, 4...Control unit, 31...Adding unit, 34...First filter (filter), 36...Second filter (filter), A...Actuator (suspension device), B...Sprung member, W...Unsprung member

Claims

1. A sprung speed detection unit that detects the vertical sprung speed of the sprung member in a vehicle, A control unit controls a suspension device in the aforementioned vehicle, which is interposed in parallel with a passive shock absorber between the sprung mass member and the unsprung mass member and capable of generating a control force to suppress vibration of the sprung mass member, based on the sprung mass speed. The system includes a signal processing unit that processes the sprung speed signal and, in the frequency characteristics of the gain from the signal input to the control unit to the sprung speed output by the sprung speed detection unit, widens the frequency band in which the gain of the sprung speed signal after processing exceeds a predetermined reference value, including the sprung resonance frequency, compared to the frequency band in which the gain of the sprung speed signal before processing exceeds a predetermined reference value. The control unit controls the suspension device based on the signal of the sprung speed after the processing. A suspension control device characterized by the following features.

2. A sprung speed detection unit that detects the vertical sprung speed of the sprung member in a vehicle, A control unit controls a suspension device having a damping element, which is interposed between the sprung mass member and the unsprung mass member in the vehicle and capable of generating a control force to suppress vibration of the sprung mass member, based on the sprung mass speed. The system includes a signal processing unit that processes the sprung speed signal and, in the frequency characteristics of the gain from the signal input to the control unit to the sprung speed output by the sprung speed detection unit, widens the frequency band in which the gain of the sprung speed signal after processing exceeds a predetermined reference value, including the sprung resonance frequency, compared to the frequency band in which the gain of the sprung speed signal before processing exceeds a predetermined reference value. The control unit controls the suspension device based on the signal of the sprung speed after the processing. A suspension control device characterized by the following features.

3. The signal processing unit sets the reference value to 0 dB and widens the frequency band in which the gain of the sprung speed signal after processing is 0 dB or more than the frequency band in which the gain of the sprung speed signal before processing is 0 dB or more. The suspension control device according to claim 1 or 2, characterized by the above.

4. The signal processing unit, Without changing the lower limit of the frequency band in which the gain of the sprung-load velocity signal after the above processing is 0 dB or more, the upper limit is brought closer to the unsprung-load resonance frequency band than the upper limit of the frequency band in which the gain of the sprung-load velocity signal before the above processing is 0 dB or more. The suspension control device according to claim 3.

5. The signal processing unit, The upper limit of the frequency band in which the gain of the sprung-load velocity signal after the above processing is 0 dB or higher is set to 5 Hz, bringing it closer to the unsprung-load resonance frequency band. The suspension control device according to feature 4.

6. The signal processing unit includes one or more filters that filter the signal of the sprung speed before processing. The suspension control device according to claim 1 or 2, characterized by the above.

7. The signal processing unit, A first filter that filters the signal of the spring velocity before the aforementioned processing, A second filter filters the sprung velocity signal processed by the first filter, The system includes an adder that adds the signal of the sprung velocity before the aforementioned processing and the signals of each sprung velocity filtered by the first filter and the second filter, The suspension control device according to claim 1 or 2, characterized by the above.

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