JP2007015633A - Abnormality determination device for stroke sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely determine abnormalities of stroke sensors regardless of deviation of live load of a vehicle even when the vehicle is running. <P>SOLUTION: An integrating means M2 integrates output of the front and rear stroke sensors SbF, SbR for predetermined time, and a deviation calculating means M3 calculates deviation of an integral value of the output of the front and rear stroke sensors SbF, SbR. Since an abnormality determining means M4 determines abnormalities of the front and rear stroke sensors SbF, SbR when the deviation calculated by the deviation calculating means M3 exceeds a threshold value, the abnormality determining means M4 can securely determine the abnormalities even if live load of the vehicle is deviated and even if a stroke of a wheel is changed during running of the vehicle. When a strait running state determining means M5 determines that the vehicle is in a strait running state, or that front and rear wheels pass through the same position on a road surface, the abnormality determining means M4 determines abnormalities. Therefore, accuracy of abnormality determination can be enhanced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an abnormality determination device for a stroke sensor that determines an abnormality of a front and rear stroke sensor that detects a vertical stroke of a front wheel and a rear wheel with respect to a vehicle body.

When traction control is performed based on the speed difference between the driving wheel and the driven wheel, the control value of the traction control is corrected based on the stroke difference between the wheels, thereby improving the stability and maneuverability of the vehicle during travel. In addition, in what improves the ride comfort, it is known from Japanese Patent Application Laid-Open Publication No. 2005-228959 that determines a system abnormality when the stroke difference of each wheel exceeds a reference value.
JP-A-5-270300

  By the way, since the stroke difference of each wheel greatly changes due to the deviation of the load of the vehicle, it is not possible to make a highly accurate determination simply by determining the system abnormality when the stroke difference of each wheel exceeds the reference value. Have difficulty. Moreover, since the stroke of each wheel individually increases or decreases while the vehicle is running, it is more difficult to determine an abnormality based on the stroke difference of each wheel.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to make it possible to reliably determine an abnormality of a stroke sensor regardless of a deviation in a load of a vehicle and even when the vehicle is traveling. .

  In order to achieve the above object, according to the first aspect of the present invention, an abnormality determination device for a stroke sensor that determines an abnormality of a front and rear stroke sensor that detects the vertical strokes of the front and rear wheels with respect to the vehicle body, respectively. , The integration means for integrating the output of the front and rear stroke sensors over a predetermined time, the deviation calculation means for calculating the deviation of the integrated value of the output of the front and rear stroke sensors, and the deviation calculated by the deviation calculation means is greater than or equal to the threshold value There is proposed an abnormality determination device for a stroke sensor, characterized by comprising an abnormality determination means for determining abnormality at the time.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the abnormality determination means determines an abnormality when the vehicle is in a straight traveling state. A device is proposed.

  According to the invention described in claim 3, in addition to the configuration of claim 1 or 2, the sprung acceleration sensor for detecting sprung acceleration at the position of the front wheel and the rear wheel, and the sprung acceleration sensor, respectively. By comparing the output of the front and rear stroke sensors with the output of the stroke state estimating means when the abnormality determining means determines abnormality, the stroke state estimating means for estimating the front wheel and rear wheel stroke states from the output of A stroke sensor abnormality determination device is provided, characterized by comprising stroke sensor identification means for identifying a stroke sensor in which an abnormality has occurred.

  The unsprung speed estimation means M7 of the embodiment corresponds to the stroke state estimation means of the present invention.

  According to the configuration of the first aspect, the integrating means integrates the outputs of the front and rear stroke sensors over a predetermined time, the deviation calculating means calculates the deviation of the integrated value of the outputs of the front and rear stroke sensors, and the abnormality determining means. Is detected when the deviation calculated by the deviation calculating means is equal to or greater than the threshold, even if the vehicle load is uneven or the vehicle is running and the wheel stroke is changing. The abnormality of the stroke sensor can be reliably determined.

  According to the configuration of the second aspect, when the vehicle is in a straight traveling state, that is, when the front wheels and the rear wheels pass through the same position on the road surface, the deviation of the integrated value of the output of the front and rear stroke sensors is calculated. Since the abnormality determination means determines abnormality based on the above, the accuracy of abnormality determination can be improved.

  According to the configuration of claim 3, the stroke state estimating means estimates the stroke states of the front wheels and the rear wheels based on the sprung accelerations at the positions of the front wheels and the rear wheels respectively detected by the front and rear sprung acceleration sensors, and an abnormality determination is made. When the means determines abnormality, the stroke sensor specifying means identifies which of the front and rear stroke sensors has an abnormality by comparing the output of the front and rear stroke sensors and the output of the stroke state estimating means. be able to.

  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 view showing a model of a suspension. 4 is an explanatory diagram of skyhook control, FIG. 5 is a block diagram of a stroke sensor abnormality determination device, and FIG. 6 is a block diagram of unsprung speed estimation means.

  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 signals from sprung acceleration sensors SaF and SaR that detect sprung acceleration, signals from stroke sensors SbF and SbR that detect the stroke of the damper 14, and A signal from the vehicle speed sensor Sc that detects the vehicle speed and a signal from the yaw rate sensor Sd that detects the yaw rate are input.

  The subscript “F” of the sprung acceleration sensors SaF and SaR and the stroke sensors SbF and SbR indicates a front wheel sensor, and the subscript “R” indicates a rear wheel sensor.

  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, if the coil 28 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passage 22a of the piston 22 increases and it becomes 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 sensors SaF and SaR, the stroke of the damper 14 detected by the stroke sensors SbF and SbR, the vehicle speed detected by the vehicle speed sensor Sc, and the yaw rate sensor Sd. Based on the yaw rate, etc., by controlling the damping force of each of the four dampers 14 of each wheel W individually, the skyhook control of the vehicle that suppresses the swaying of the vehicle when overcoming the unevenness of the road surface and enhances the ride comfort The ride comfort control and the steering stability control that suppresses the rolling during the turning of the vehicle and the pitching during the sudden acceleration and deceleration of the vehicle are selectively executed according to the driving state of the vehicle, and the stroke sensor SbF. , SbR abnormality is determined.

  Next, based on FIG. 3 and FIG. 4, the skyhook control for suppressing the vehicle shake and enhancing the ride comfort will be described.

  As apparent from the suspension device model shown in FIG. 3, an unsprung mass 18 is connected to the road surface via a virtual spring 17 of the tire, and the unsprung mass 18 is coupled to the unsprung mass 18 via the damper 14 and the coil spring 15. 19 is connected. The damping force of the damper 14 is variable by energizing the coil 28. The rate of change dX2 / dt of the displacement X2 of the sprung mass 19 corresponds to the sprung speed obtained by integrating the sprung acceleration output detected by the sprung acceleration sensors SaF and SaR. The rate of change d (X2−X1) / dt of the difference between the displacement X2 of the sprung mass 19 and the displacement X1 of the unsprung mass 18 corresponds to a damper speed obtained by differentiating the outputs of the stroke sensors SbF and SbR.

dX2 / dt × d (X2−X1) / dt> 0
In this case, that is, when the sprung speed and the damper speed are in the same direction (same sign), the damper 14 is controlled to increase the damping force. on the other hand,
dX2 / dt × d (X2−X1) / dt ≦ 0
In this case, that is, when the sprung speed and the damper speed are in opposite directions (reverse signs), the damper 14 is controlled in a direction to reduce the damping force.

  Therefore, considering the case where the wheel W passes over the protrusion on the road surface as shown in FIG. 4, the vehicle body 11 moves upward while the wheel W ascends along the first half of the protrusion as shown in (1). The sprung speed (dX2 / dt) becomes a positive value, the damper 14 is compressed, and the damper speed d (X2-X1) / dt becomes a negative value. Controlled to reduce damping force.

  Also, as shown in (2), immediately after the wheel W passes over the top of the protrusion, the vehicle body 11 still moves upward due to inertia, and the sprung speed (dX2 / dt) becomes a positive value. Since the damper 14 is extended and the damper speed d (X2-X1) / dt becomes a positive value, the damper 14 is controlled to have the same sign and increase the damping force in the extension direction.

  Further, as shown in (3), while the wheel W descends along the latter half of the protrusion, the vehicle body 11 moves downward and the sprung speed (dX2 / dt) becomes a negative value. Since the damper 14 is extended faster and the damper speed d (X2-X1) / dt becomes a positive value, both are reversed in sign and the damper 14 is controlled to reduce the damping force in the extension direction. Is done.

  Also, as shown in (4), immediately after the wheel W has completely passed over the protrusion, the vehicle body 11 still moves downward due to inertia, and the sprung speed (dX2 / dt) becomes negative, and the wheel W is lowered. By stopping, the damper 14 is compressed and the damper speed d (X2−X1) / dt becomes a negative value. Therefore, the damper 14 is controlled to have the same sign and increase the damping force in the compression direction. .

  Next, the configuration and operation of the stroke sensor abnormality determination device Ua in the electronic control unit U will be described.

  As shown in FIG. 5, the stroke sensor abnormality determining device Ua includes a high-pass filter M1, an integrating means M2, a deviation calculating means M3, an abnormality determining means M4, a straight traveling state determining means M5, a high-pass filter M6, An unsprung speed estimating means M7, a differentiating means M8, and a stroke sensor specifying means M9 are provided. The stroke sensor abnormality determination device Ua determines the abnormality of the stroke sensors SbF and SbR provided on the front wheel and rear wheel dampers 14 and 14 with the left front wheel and rear wheel (or right front wheel and rear wheel) as a pair. To do.

  The outputs of the front and rear stroke sensors SbF and SbR are passed through the high-pass filter M1, and for example, a pitch resonance component and a roll resonance component on a spring having a frequency of 3 Hz or less are cut. The integrating means M2 separately integrates the outputs of the stroke sensors SbF and SbR before and after passing through the high-pass filter M1. The integration is reset every predetermined time (for example, 5 seconds), and the past four integration values are sequentially updated and stored. The deviation calculating means M3 calculates a deviation between the integrated value of the output of the front stroke sensor SbF and the integrated value of the output of the rear stroke sensor SbR calculated simultaneously. The abnormality determination means M4 increments the counter when the deviation is equal to or greater than a preset threshold value.

  However, the abnormality determination means increments the counter by M4 on the condition that the vehicle is in a straight traveling state. If the vehicle is in a turning state, even if the deviation exceeds a preset threshold value. The counter is not incremented. In other words, the straight traveling state determination means M5 is configured such that the vehicle travels straight when the vehicle speed detected by the vehicle speed sensor Sc is 25 km / h or more or the yaw rate detected by the yaw rate sensor Sd is 0.05 rad / s or less. It is considered to be in a state and the counter is allowed to increment. The reason is that when the vehicle speed is less than 25 km / h or the yaw rate exceeds 0.05 rad / s, the front and rear wheels are unlikely to pass the same position on the road surface, so the front and rear stroke sensors SbF, This is because even if the SbR is normal, the deviation of the integrated values of those outputs may be greater than or equal to the threshold value.

  Accordingly, the abnormality determination means M4 determines whether the front and rear stroke sensors SbF and SbR are output when the deviation of the integrated value of the outputs of the front and rear stroke sensors SbF and SbR becomes equal to or greater than the threshold value for a predetermined number of times (four in the embodiment). It is determined that an abnormality has occurred in at least one of the above.

  FIG. 6 is a block diagram of the unsprung speed estimation means M7, and the gains A, K, Ca, and C in the figure are shown in Equations 1 to 4, respectively.

  The parameters in Equations 1 to 4 are shown in FIG. 3, where m1 is the unsprung mass, m2 is the sprung mass, Ka is the spring constant of the virtual spring 17 of the tire, Kb is the spring constant of the coil spring 15, Cb is a damping coefficient of the damper 14.

  In this way, by processing the unsprung acceleration before and after passing through the high-pass filter M6 by the unsprung speed estimation means M7, the estimated unsprung speed before and after can be obtained.

  Which of the front and rear stroke sensors SbF and SbR becomes abnormal can be determined as follows. That is, the stroke sensor specifying means M9 compares the estimated unsprung speed before and after estimated by the unsprung speed estimation means M7 and the actual unsprung speed before and after obtained by differentiating the output of the high-pass filter M1 by the differentiating means M8. Therefore, it can be determined that the stroke sensors SbF and SbR that match each other are normal and the stroke sensors SbF and SbR that do not match each other are abnormal.

  As described above, the deviation of the integral value obtained by integrating the outputs of the front and rear stroke sensors SbF and SbR over a predetermined time is calculated, and one of the stroke sensors SbF and SbR is abnormal when the deviation is equal to or greater than the threshold value. Therefore, even if the load on the vehicle is uneven or the vehicle is running and the stroke of the wheel is changed, it is possible to reliably determine the abnormality.

  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.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Diagram showing suspension model Illustration of skyhook control Block diagram of stroke sensor abnormality determination device Block diagram of unsprung speed estimation means

Explanation of symbols

SaF Sprung acceleration sensor SaR Sprung acceleration sensor SbF Stroke sensor SbR Stroke sensor M2 Integrating means M3 Deviation calculating means M4 Abnormality determining means M7 Unsprung speed estimating means (stroke state estimating means)
M9 Stroke sensor identification means

Claims (3)

In an abnormality determination device for a stroke sensor for determining an abnormality of a front and rear stroke sensor (SbF, SbR) for detecting a vertical stroke with respect to a front wheel and a rear wheel, respectively,
Integrating means (M2) for integrating the outputs of the front and rear stroke sensors (SbF, SbR) over a predetermined time period;
Deviation calculation means (M3) for calculating the deviation of the integrated value of the outputs of the front and rear stroke sensors (SbF, SbR);
An abnormality determining means (M4) for determining an abnormality when the deviation calculated by the deviation calculating means (M3) is equal to or greater than a threshold;
An abnormality determination device for a stroke sensor, comprising:   The abnormality determination device for a stroke sensor according to claim 1, wherein the abnormality determination means (M4) determines an abnormality when the vehicle is in a straight traveling state. Sprung acceleration sensors (SaF, SaR) for detecting sprung acceleration at the positions of the front wheel and the rear wheel,
Stroke state estimating means (M7) for estimating the stroke states of the front wheels and the rear wheels from the output of the sprung acceleration sensor (SaF, SaR);
When the abnormality determination means (M4) determines an abnormality, the stroke sensor (SbF) where the abnormality has occurred is compared by comparing the outputs of the front and rear stroke sensors (SbF, SbR) with the output of the stroke state estimation means (M7). , SbR), a stroke sensor specifying means (M9);
The stroke sensor abnormality determination device according to claim 1, wherein the abnormality determination device is provided.

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