JP2006273222A - Controlling device for adjustable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove effects of a high frequency noise added to the control input for controlling the damping force of a damper of a suspension device by a simplest constitution. <P>SOLUTION: When a target current for adjusting the damping force of the damper of the suspension device is determined based on a damper speed which is obtained by the time-differentiation of a damper displacement, as the high frequency noise is added in a procedure for obtaining the damper rate, the high frequency noise is added to the target current which is determined by using the damper rate as well, and the switching of the damping force of the damper is frequently performed, and causes noises. However, the effects of the high frequency noise are eliminated by filtering the target current by using a filter which makes a frequency in a nonsuspended resonance region of the suspension device pass, and noises can be reduced by preventing the switching of the damping force of the damper from being frequently performed. Also, the effect of a new frequency noise which is added when the target current is obtained from the damper rate can be eliminated as well, and the damping force of the damper can accurately be controlled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a variable damping force damper that variably controls a damping force of a damper provided in a suspension device of a vehicle according to a motion state of the vehicle by a control means.

  As the viscous fluid of the variable damping force damper for the suspension device, a magnetic viscous fluid (MRF: Magneto-Rheological Fluids) whose viscosity is changed by the action of a magnetic field is adopted, and the fluid is applied to the piston that is slidably fitted into the cylinder. Patent Document 1 below discloses a coil provided with a coil for applying a magnetic field to a magnetorheological fluid in a passage. According to this variable damping force damper, the damping force of the damper can be arbitrarily controlled by changing the viscosity of the magnetorheological fluid in the fluid passage by a magnetic field generated by energizing the coil.

In order to perform skyhook control, the unsprung speed is calculated from the damper displacement and the output of the sprung acceleration sensor, and the unsprung speed is corrected by applying a filter that passes only vibrations in the unsprung resonance frequency range to the unsprung speed. Japanese Patent Application Laid-Open Publication No. 2004-228561 calculates the unsprung required damping force of a damper using
JP-A-60-113711 JP-A-8-268025

  By the way, when calculating the damper speed by differentiating the damper displacement detected by the damper displacement sensor through a differential filter with time, and calculating the target current supplied to the damper by map search using this damper speed, Designing a differential filter that minimizes the phase delay to ensure control up to the resonance frequency range inevitably causes some high-frequency noise to be applied to the output damper speed. High frequency noise gets on. Therefore, when the damping force of the damper is controlled with this target current, there is a problem that the damping force of the damper is frequently switched due to the influence of high-frequency noise and causes noise.

  Therefore, it is conceivable to perform a map search for the target current based on the damper speed after removing the high-frequency noise by applying a low-pass filter to the damper speed on which the high-frequency noise is mounted. Since linear high frequency noise is carried, there is a problem that the accuracy of the target current is lowered.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to eliminate the influence of high-frequency noise on a control amount for controlling the damping force of a damper of a suspension device with the simplest configuration.

  In order to achieve the above object, according to the first aspect of the present invention, the damper speed obtained by differentiating the damper displacement with respect to the control amount for adjusting the damping force of the damper provided in the suspension device of the vehicle. A control apparatus for a variable damping force damper, wherein the control amount is filtered using a filter that passes the frequency of the unsprung resonance region of the suspension device. A device is proposed.

  According to a second aspect of the invention, in addition to the configuration of the first aspect, the filter is a low-pass filter that allows a frequency of 15 Hz or less to pass therethrough. Proposed.

  The target current It of the embodiment corresponds to the control amount of the present invention.

  According to the above configuration, when the control amount for adjusting the damping force of the damper provided in the vehicle suspension device is determined based on the damper speed obtained by differentiating the damper displacement with respect to time, high-frequency noise is generated in the process of determining the damper speed. Since riding is inevitable, high-frequency noise also rides on the control amount determined using this damper speed, and the damping force of the damper is frequently switched, causing noise. However, the influence of high frequency noise is removed by filtering the control amount using a filter that passes the frequency of the unsprung resonance region of the suspension device, specifically, a frequency of 15 Hz or less, and the damping force of the damper can be switched. It is possible to prevent frequent occurrence and reduce noise. In addition, the influence of new high-frequency noise on the occasion of obtaining the control amount from the damper speed can be removed, and the damping force of the damper can be controlled with high accuracy.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 6 show an embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension device, FIG. 2 is an enlarged sectional view of a variable damping force damper, and FIG. 3 is a flowchart of damping force control of the damper. 4 is a map for searching for the target current from the damper speed and the target damping force, FIG. 5 is a graph showing the filtering characteristics of the low-pass filter, and FIG. 6 is a graph showing the waveform of the target current before and after filtering.

  As shown in FIG. 1, a suspension device S that suspends a wheel W of a four-wheeled vehicle has a suspension arm 13 that supports a knuckle 12 in a vertically movable manner on a vehicle body 11, and a variable damping that connects the suspension arm 13 and the vehicle body 11. A force damper 14 and a coil spring 15 connecting the suspension arm 13 and the vehicle body 11 are provided. The electronic control unit U that controls the damping force of the damper 14 includes a signal from the sprung acceleration sensor Sa that detects the sprung acceleration, a signal from the damper displacement sensor Sb that detects the displacement (stroke) of the damper 14, and A signal from the lateral acceleration sensor Sc that detects the lateral acceleration of the vehicle and a signal from the vehicle speed sensor Sd that detects the vehicle speed are input.

  As shown in FIG. 2, the damper 14 includes a cylinder 21 whose lower end is connected to the suspension arm 13, a piston 22 that is slidably fitted into the cylinder 21, and an upper wall of the cylinder 21 that extends upward from the piston 22. And a free piston 24 that is slidably fitted to the lower part of the cylinder, and is partitioned by the piston 22 inside the cylinder 21. An upper first fluid chamber 25 and a lower second fluid chamber 26 are partitioned, and a gas chamber 27 in which a compressed gas is sealed in a lower portion of the free piston 24 is partitioned.

  A plurality of fluid passages 22a are formed in the piston 22 so that the upper and lower surfaces thereof communicate with each other, and the first and second fluid chambers 25 and 26 communicate with each other through these fluid passages 22a. The magnetorheological fluid sealed in the first and second fluid chambers 25 and 26 and the fluid passages 22a is a dispersion of magnetic fine particles such as iron powder in a viscous fluid such as oil. By aligning the magnetic fine particles along the magnetic field lines, it is difficult for the viscous fluid to flow, and the apparent viscosity increases. A coil 28 is provided inside the piston 22, and energization of the coil 28 is controlled by the electronic control unit U. When the coil 28 is energized, a magnetic flux is generated as indicated by an arrow, and the viscosity of the magnetorheological fluid changes due to the magnetic flux passing through the fluid passages 22a.

  When the damper 14 contracts and the piston 22 moves downward with respect to the cylinder 21, the volume of the first fluid chamber 25 increases and the volume of the second fluid chamber 26 decreases. Passes through the fluid passage 22a of the piston 22 and flows into the first fluid chamber 25. Conversely, when the damper 14 extends and the piston 22 moves upward relative to the cylinder 21, the volume of the second fluid chamber 26 increases. Since the volume of the first fluid chamber 25 decreases, the magnetorheological fluid in the first fluid chamber 25 passes through the fluid passage 22a ... of the piston 22 and flows into the second fluid chamber 26, and at that time, the fluid passage 22a The damper 14 generates a damping force due to the viscous resistance of the magnetorheological fluid passing through.

  At this time, when the coil 28 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passages 22a of the piston 22 increases, making it difficult to pass through the fluid passage 22a. Damping force increases. The increase amount of the damping force can be arbitrarily controlled by the magnitude of the current supplied to the coil 28.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 26, the free piston 24 descends while the gas chamber 27 is contracted to absorb the impact. Further, when a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 26, the impact is absorbed by the free piston 24 rising while the gas chamber 27 is expanded. Further, when the piston 22 descends and the volume of the piston rod 23 accommodated in the cylinder 21 increases, the free piston 24 descends so as to absorb the increase in the volume.

  Thus, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sa, the damper displacement detected by the damper displacement sensor Sb, the lateral acceleration detected by the lateral acceleration sensor Sc (or the vehicle speed detected by the vehicle speed sensor Sd). Based on the above, by controlling the damping force of each of the four dampers 14 of each wheel W individually, such as skyhook control that increases the ride comfort by suppressing the vehicle swaying when overcoming the road surface unevenness Ride comfort control and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration and deceleration of the vehicle are selectively executed according to the driving state of the vehicle.

  FIG. 3 shows a flowchart for explaining the operation of the steering stability control that suppresses rolling by increasing the damping force of the dampers 14 when the vehicle turns.

  First, in step S1, the lateral acceleration YG detected by the lateral acceleration sensor Sc is time-differentiated to calculate a lateral acceleration differential value dYG / dt, and the lateral acceleration differential value dYG / dt is multiplied by a gain Gain to be generated in the damper 14. The power target damping force Ft is calculated. In the subsequent step S2, the damper speed Vp is calculated by differentiating the damper displacement detected by the damper displacement sensor Sb with respect to time. In the following step S3, the target current It is searched by applying the target damping force Ft and the damper speed Vp to the map of FIG. In step S4, the target current It is supplied to the coil of the damper 14 to generate the target damping force Ft, thereby suppressing rolling of the vehicle and improving the steering stability performance.

  FIG. 4 is a map for retrieving the target current It from the target damping force Ft and the damper speed Vp. When the damper speed Vp is constant, the target current It increases as the target damping force Ft increases. When the force Ft is constant, the target current It decreases as the damper speed Vp increases. For example, when the target damping force Ft is Ft1 and the damper speed Vp is Vpt, the target current is It5, but when the damper speed Vp increases to Vpt1, the target current decreases to It4 and the damper speed Vp decreases to Vpt2. Then, the target current increases to It6.

  Incidentally, the damper speed Vp, which is a parameter on the horizontal axis of the map of FIG. 4, corresponds to a time-differentiated damper displacement detected by the damper displacement sensor Sb through a differential filter. If the differential filter is designed so as to minimize the phase delay in order to reliably perform the above, it is inevitable that a certain amount of high-frequency noise is applied to the output damper speed Vp. Conventionally, the target current It is searched from the map of FIG. 4 after passing the damper speed Vp on which the high-frequency noise is applied through a low-pass filter to remove the high-frequency noise component. In this embodiment, the high-frequency noise is applied. The target current It is searched by applying the damper speed Vp as it is to the map of FIG.

  The thin line in FIG. 6 shows the waveform of the target current It obtained as described above, and it can be seen that the target current It also has high frequency noise due to the high frequency noise of the damper speed Vp. Therefore, the target current It carrying high-frequency noise is passed through the low-pass filter shown in FIG. 5, and only the vibration waveform of 15 Hz or less corresponding to the resonance frequency of the unsprung resonance region of the suspension S is extracted. The thick line in FIG. 6 shows the waveform of the target current It passed through the low-pass filter, and it can be seen that the waveform of the unsprung resonance region is extracted by removing the high frequency component. Therefore, by controlling the damping force of the damper 14 with the target current It, it is possible to accurately perform the steering stability control that suppresses rolling of the vehicle, and to increase the switching frequency of the damping force of the damper 14 due to the high frequency noise. It can contribute to noise reduction by suppressing.

  Further, when the damper displacement detected by the damper displacement sensor Sb is passed through the differential filter to obtain the damper speed Vp, a certain amount of noise can be allowed. Therefore, the phase of the damper speed Vp is determined using a differential filter with little phase delay. Delay can be minimized. Further, since a low-pass filter is disposed at the final stage of the process of obtaining the target current It, noise generated during map search can be removed by this low-pass filter.

  The ride comfort control when the above-described steering stability control is not performed is the well-known skyhook control, and when the sprung speed (upward is positive) and the damper speed (extension direction is positive) are the same direction. The dampers 14 are controlled to increase the damping force. When the sprung speed and the damper speed are opposite directions, the dampers 14 are controlled to decrease the damping force. The sprung speed can be obtained by integrating the sprung acceleration detected by the sprung acceleration sensor Sa, and the damper speed can be obtained by differentiating the damper displacement detected by the damper displacement sensor Sb.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the steering stability control that suppresses the rolling of the vehicle based on the lateral acceleration differential value dYG / dt obtained by time-differentiating the lateral acceleration YG detected by the lateral acceleration sensor Sc has been described. However, the present invention provides the vehicle speed sensor Sd. The present invention can also be applied to steering stability control that suppresses pitching of the vehicle based on the longitudinal acceleration differential value dXG / dt obtained by differentiating the detected vehicle speed by the second floor time.

  In the embodiment, the damping force of the dampers 14 is variably controlled using a magnetorheological fluid, but any method for variably controlling the damping force is arbitrary.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Flow chart of damper damping force control Map to search for target current from damper speed and target damping force Graph showing the filtering characteristics of a low-pass filter Graph showing the waveform of the target current before and after filtering

Explanation of symbols

14 Damper It Control amount (Target current)
S suspension device

Claims (2)

Variable damping force for determining a control amount (It) for adjusting the damping force of the damper (14) provided in the vehicle suspension device (S) based on the damper speed (Vp) obtained by differentiating the damper displacement over time A damper control device,
A control device for a variable damping force damper, wherein the control amount (It) is filtered using a filter that allows the frequency of the unsprung resonance region of the suspension device (S) to pass through. The control device for a variable damping force damper according to claim 1, wherein the filter is a low-pass filter that passes a frequency of 15 Hz or less.

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