Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1997-12-22
2001-01-30
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S070000, C701S078000, C701S071000, C701S080000, C303S122000, C303S136000, C303S146000, C303S191000, C702S140000, C702S183000
Reexamination Certificate
active
06182001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diagnostic apparatus for a dynamic system, and more particularly, to an apparatus for very accurately diagnosing faults in a dynamic system, the air pressure of a tire, and conditions around the tire by vibrating the dynamic system through use of vibration means provided in the diagnostic apparatus and on the basis of internal disturbance caused by a fault in the thus-vibrated dynamic system even in a case where the amount of external disturbance is small.
Further, the present invention relates to a braking pressure estimation device which estimates master cylinder pressure, mean braking pressure, and a micro-vibration component in the braking pressure on the basis of wheel speed information and without use of a braking pressure sensor, by taking note of the gain characteristics of a wheel speed and the braking pressure in a case where the braking pressure is minutely vibrated at a resonance frequency of a vibration system comprised of a vehicle body, a wheel, and a road surface. Still further, the present invention relates to an anti-lock brake controller which employs the braking pressure estimation device, as well as to a braking pressure controller capable of continually controlling braking pressure in a smooth manner.
2. Related Art
(Conventional Apparatus for Diagnosing a Dynamic System)
Japanese Patent Application Laid-open (JP-A) No. 7-98268 describes the following technique as an apparatus for diagnosing a dynamic system.
In the technique disclosed in the foregoing unexamined patent application, a total disturbance vector—which is the sum of an external disturbance vector exerted on a dynamic system from outside and an internal disturbance vector caused by a fault in the dynamic system—is estimated on the basis of a response output vector from the dynamic system. Further, an internal state quantity vector of the dynamic system is estimated. A component relevant to internal disturbance is separated from the total disturbance vector by calculation of the correlation between the thus-estimated total disturbance vector and the internal state quantity vector. Then, a part of the dynamic system corresponding to the thus-separated component relevant to the internal disturbance is specified as a fault.
The foregoing technique enables location of an area of the dynamic system to be examined through use of one observer, as well as estimation of the absence or presence of a fault in the area and the degree of the fault. As contrasted with a conventional generalized likelihood comparison test method, there is no need for this technique to examine a plurality of areas through use of a plurality of observers disposed so as to correspond to the areas, and hence the technique has an advantage of being capable of accurately sensing a fault with few calculations.
(Conventional Braking Pressure Estimation Device, and Anti-lock Brake Controller Utilizing the Braking Pressure Estimation Device)
With regard to a device which controls the braking force of wheels such as an anti-lock brake controller (hereinafter referred to as an ABS controller), the sensing of braking pressure is an important problem, and a higher degree of control of the braking pressure can be expected if the value of the braking pressure is known. As a method for sensing the braking pressure, there is a method of attaching pressure sensors comprising a semiconductor device or the like to each wheel cylinder. However, the pressure sensors are comparatively expensive, and attachment of the pressure sensors to each wheel cylinders is difficult in terms of cost.
To overcome such a difficulty, there has already been proposed a technique of estimating the wheel cylinder pressure of each wheel on the basis of the result of measurement of the pressure sensor attached to the master cylinder pressure. Japanese Patent Application Laid-open (JP-A) No. 7-186918 describes a braking pressure controller which employs a method of calculating the wheel cylinder pressure of each wheel from a measured supply pressure (e.g., master cylinder pressure) and the time period over which a valve is actuated. This method enables the estimation of the wheel cylinder pressure of each wheel solely by sensing the pressure of the master cylinder through use of one pressure sensor, thereby rendering the braking pressure controller advantageous in terms of cost.
However, in many widely-available ABS controllers, a pressure sensor is not attached even to the master cylinder. Therefore, even the foregoing wheel cylinder estimation technique that requires the attachment of a pressure sensor to only the master cylinder still adds to the cost. Further, there is needed a remedy for sensor failures in order to ensure the reliability of the pressure sensor, which also adds to the cost.
Japanese Patent Application Laid-open (JP-A) No. 6-286590 describes a method of estimating master cylinder pressure without use of a pressure sensor.
The technique described in the foregoing patent application discloses the following three methods for estimating master cylinder pressure.
(1) Assuming that there is a uniform increase in the master cylinder pressure as a result of a first reduction in hydraulic braking pressure, a variation &Dgr;Pm (constant) in the master cylinder pressure is calculated. The master cylinder pressure is corrected through use of the thus—calculated variation &Dgr;Pm.
(2) By utilization of a tendency for the variation in the master cylinder pressure to increase in accordance with a variation &Dgr;S in slip rate so long as the value of the master cylinder pressure is large, the variation &Dgr;Pm in the master cylinder pressure is calculated from the variation in the slip rate. Accordingly, as contrasted with the method described in (1) which is based on the assumption that the variation in the master cylinder pressure is constant, degree of accuracy of estimation is improved.
(3) The variation &Dgr;Pm in the master cylinder is calculated from a variation &Dgr;V′
w0
in vehicle acceleration and the variation &Dgr;S in the slip rate. The use of the variation &Dgr;V′
w0
in vehicle acceleration enables correction of the master cylinder pressure, even when slippage of wheels due to speed reduction has not yet occurred and therefore the master cylinder pressure Pm is low. Accordingly, as contrasted with the method described in (2), this method further improves the accuracy of estimation of master cylinder pressure.
(Conventional Hydraulic Braking Pressure Controller)
For an apparatus such as an ABS controller in which the braking force applied to the vehicle is controlled by the hydraulic pressure of the wheel cylinder, not only a reduction in the hydraulic braking pressure at the time of wheel lock, but also smooth continuous control of the hydraulic braking pressure is important.
The hydraulic braking pressure is controlled by pressure increase and decrease valves (such as those disposed in an ABS actuator shown in
FIGS. 23A and 23B
) that are controllable from outside by means of an electrical signal, or the like, and are interposed between the master cylinder—whose pressure is related to the depression of a brake pedal given by the driver—and the wheel cylinders which produce pressure for pressing brake pads; i.e., the actual braking force of the vehicle.
Under normal conditions, the pressure in the master cylinder is directly transmitted to the hydraulic pressure in the wheel cylinders by opening the pressure increase valves of the ABS actuator shown in
FIGS. 23A and 23B
, as well as by closing the pressure decrease valves of the same. If the hydraulic pressure in the wheel cylinders is excessively high, there is established a state (a pressure decrease mode) in which the pressure increase valve is closed and the pressure decrease valve is opened so that the pressure from the master cylinder is prevented from being transmitted to the wheel cylinders while the hydraulic pressure in the wheel cylinders is released to a reservoir tank. In order to allow
Asano Katsuhiro
Ono Eiichi
Sugai Masaru
Umeno Takaji
Yamaguchi Hiroyuki
Kabushiki Kaisha Toyota Chuo Kenkyusho
Louis-Jacques Jacques H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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