JPH04183679A - Vehicle speed detecting device - Google Patents

Abstract

PURPOSE:To make selection and output of proper sensor output possible even when abnormality happened in one sensor by providing a selecting means that selects the detected output of one sensor among plural vehicle speed sensors and outputs it, and controlling it so as to select sensor output whose rate of change is small. CONSTITUTION:Detected outputs V1, V2 of respective sensors 1 and 2 provided to front and rear wheels as plural vehicle speed sensors are impressed to a selecting means 3, and detected output V1 of the sensor 1 is output as a vehicle speed signal Vo at the normal time when abnormality is not observed in both sensor outputs, when it is detected by an output change detecting means 4 whether or not any change happened in either of the two sensor outputs from the outputs V1, V2 of both sensors and KV1, KV2 obtained by multiplying these outputs by a coefficient K with coefficient multipliers 5 and 6. When abnormality happened in one of these sensor outputs, the selecting means 3 is controlled by a selection control means 7 so as to respond to the output of the output change detecting means 4, compare the absolute values of the rates of change of the outputs of the sensors 1, 2 obtained by a change rate calculating means 8, and make the output of the sensor whose absolute value of rate of change is smaller to the vehicle speed signal Vo.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vehicle speed detection device that has a plurality of vehicle speed sensors and is capable of dealing with a failure of the vehicle speed sensors.

[Conventional technology]

Generally, vehicles are equipped with a vehicle speed sensor and operate and control various driving states according to the vehicle speed. However, if the vehicle speed sensor malfunctions, the specified operations and controls cannot be performed, and such a situation may cause the vehicle to Since it impairs the safety of the vehicle, countermeasures must be taken against the failure of the vehicle speed sensor. Therefore, in the past, multiple vehicle speed sensors were installed so that even if one of them failed, the output of a healthy vehicle speed sensor would be used. A method has been proposed in which the output of the sensor with the largest output among the outputs of the sensors is extracted (see Japanese Patent Laid-Open No. 146775/1983).

That is, as shown in FIG. 4(a), the outputs v1. of the two vehicle speed sensors 1 and 2. v2 is introduced into the selection means 3,
The same stage is the output of the sensor with the larger output among both sensors.
is output as the heavy speed No. Vo. The selection means 3 is realized, for example, in a control unit constituted by a microcomputer, and the selection and derivation of the vehicle speed signal by interrupt processing in the control unit is, in principle, as shown in FIG. 4(b).
The process is carried out according to the flowchart shown in , and in step 1.2, the outputs V1 and ¥2 of both sensors 1 and 2 are detected, and in step 3, the two values are compared, and the output with the larger value is used as the vehicle speed signal. .

[The problem that the invention aims to solve]

Such conventional vehicle speed detection devices obtain the larger output from among the detection outputs of multiple sensors, so even if one sensor fails and its output is lost, the system remains in good condition. However, due to superimposition of noise on the sensor detection output or a faulty part of the sensor circuit, the sensor output may become larger than the normal one. In this case, an abnormal detection output will appear as the output of the vehicle speed detection device.

Such a situation can be said to be desirable from the viewpoint of fail-sale when the vehicle speed detection device is used for operation or control that tends to suppress the vehicle speed in response to an increase in its output.

However, for example, in a vehicle with a vehicle speed-sensitive four-wheel steering system, when the output of the vehicle speed detection device is used to steer the rear wheels in the opposite phase to the front wheels at low speeds and in the same phase as the front wheels at high speeds. In this case, the abnormal detection output may cause the rear wheels to be steered in the same phase as the front wheels, even though the vehicle speed is such that the rear wheels should actually be steered in the opposite phase to the front wheels.

In a vehicle speed detection device having a plurality of vehicle speed sensors, the present invention is capable of detecting a properly healthy sensor even if an abnormality occurs in the detection output of one sensor and the detection output increases or decreases. It is an object of the present invention to provide a speed detection device capable of selectively outputting an output.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a vehicle speed detection device having a plurality of vehicle speed sensors, including a selection means for selecting and outputting the detection output of any one sensor;
Output change detection means responsive to the detection outputs of the plurality of sensors; change rate calculation means responsive to the detection outputs of the plurality of sensors; and output change detection means responsive to the outputs of the output change detection means and the change rate calculation means; and selection control means for controlling the selection means to select the detection output of the sensor with a small rate of change when an abnormality occurs in the detection output of the sensor.

[For production]

The selection means operates to select one of the plurality of vehicle speed sensors and make its detection output the output of the vehicle speed detection device. If a failure occurs in one of the sensors or noise is superimposed on the detection output, and the detection output of the sensor increases or decreases abnormally, the output change detection means generates an abnormality detection output and selects it. to the control means. The selection control means responds to this output and the change rate of each sensor output from the change rate calculation means for the detected output of each sensor, and detects a sensor with a small change rate that is a healthy and appropriate sensor. The selection means is controlled so that the selection means selects the output.

〔Example〕

An embodiment will be described with reference to the drawings. In FIG. 1, the detection outputs V1 and 2 of two sensors 1 and 2 provided on the front and rear wheels as a plurality of vehicle speed sensors are applied to the selection means 3. The means 3 outputs the detection output v1 of the sensor 1 as the vehicle speed signal Vo during normal times when no abnormality is recognized in the detection outputs of both sensors. The output change detection means 4 responds to the detection outputs of both sensors 1 and 2, and converts the outputs of both sensors 1 and 2 into coefficients of 1, for example, 0. From KVI and KV2 multiplied by 7, it is detected whether a change has occurred in the output of any of the sensors. That is, the magnitude relationship between KVl and ¥2, whether KVI<¥2 or not, and the magnitude relationship between KV2 and vl, KV2<V
A comparative judgment is made as to whether it is l or not.

If the outputs of both sensors are normal, the outputs v1 and ¥2 are equal, so KVI<¥2 and KV2<¥1 are established, and which sensor has an abnormality, for example, the output V of sensor 1
1 decreases by 30% or more, KVI<V2, but KV2<V17> (does not hold, and the output v1
When the value increases by 30% or more, since KVI<V2 does not hold, an abnormality in the sensor 1 is detected. Similarly,
Regarding the sensor 2 as well, it is possible to detect whether the output has changed abnormally depending on whether KVI<V2 and KV2<Vl hold.

The selection control means 7 responds to the output of the output change detection means 4,
When there is no abnormality in any sensor, the selection means 3 is controlled so that the output v1 of the sensor 1 is set as the vehicle speed signal Vo.

The outputs v1, V2 of the sensor 1.2 are introduced into a rate of change calculation means 8, which calculates the rate of change v1, v of both outputs with respect to time.
2 is given to the selection control means 7.

The selection control means 7 responds to the output of the output change detection means 4 when an abnormal change occurs in the output of any of the sensors, and calculates the change rate v1 of the output of the sensor 1.2 obtained from the change rate calculation means 8, 1v11 and 1v21, which are the absolute values of v2, are compared, and the selection means 3 is controlled so that the output of the sensor with the smaller absolute value of the rate of change is set as the vehicle speed signal Vo.

That is, as shown in FIG. 2, at time t1 an abnormality occurs in the output of sensor 1 and it begins to decrease, and when KV2<Vl no longer holds true at time t2, selection control means 7 controls the rate of change of both sensor outputs. Since +v2+<+vx+, the selection means 3 is controlled to set the output v2 of the sensor 2 as the vehicle speed signal VO.

FIG. 3 shows a flowchart when the present invention is implemented with a control unit configured by a microcomputer.

Upon start, outputs v1 and V2 from sensor 1.2 are detected in step 1.2, and outputs v1 and V2 are detected in step 3.4.
Each rate of change v1 and v2 of v2 is calculated. Next, in step 5, Vl is multiplied by a coefficient of, for example, 0.7, and V
2, and when 0.7Vl<V2, step 6 compares vl with the value obtained by multiplying v2 by 0.7, o, 7V2
<Vl, that is, when there is no abnormal change in the outputs of both sensors, step 7 selects the output v1 of the sensor 1 as the vehicle speed signal 0.

Then, in step 5.6, 0.7V1<V2.0.7V
If 2<Vl, move to step 8 and set MQ'll<1.
When V21, the output v1 of the sensor 1 is selected in step 7, and when IVI l > lV2 I, the output v2 of the sensor 2 is selected as the vehicle speed signal VO in step 9.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to cope with any abnormal situation in which the sensor detection output increases or decreases due to sensor failure or noise superimposition. Among them, a sensor with a small rate of change in sensor detection output is selected, so the sensor with an abnormal detection signal can be excluded and the detection output of a healthy sensor can be used as the output of the vehicle speed detection device. Operation and control in response to the output of the speed detection device can be performed safely and reliably.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing changes in the detected output of the vehicle speed sensor, Fig. 3 is a flowchart of the embodiment of the invention, and Fig. 4 is 1 is a block diagram and a flowchart of a conventional device. 1.2... Vehicle speed sensor, 3... Selection means, 4.
... Output change detection means, 5.6... Coefficient unit, 7...
Selection control means, 8... Change rate calculation means. Patent Applicant: Fuji Heavy Industries Co., Ltd. Agent, Patent Attorney: Nobu Kobashi, Ukiyo, Patent Attorney: Wataru Ogura Figures 1 and 2, Figure 3

Claims (1)

[Claims] (1) A plurality of vehicle speed sensors, a selection means for selecting and outputting the detection output of any one of the vehicle speed sensors, and output change detection responsive to the detection output of the plurality of vehicle speed sensors. means, a change rate calculation means responsive to the detection outputs of the plurality of vehicle speed sensors, and an abnormality occurring in the detection output of one of the vehicle speed sensors in response to the outputs of the output change detection means and the change rate calculation means. and selection control means for controlling the selection means to select a detection output of a sensor having a small rate of change when the change rate is small.