JP2000206128A - Wheel speed detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wheel speed detecting device to detect wheel speed with high accuracy. SOLUTION: This wheel speed detecting device is provided with an angular frequency extracting part 24y to extract angular frequency information ω from an input signal Vw from a wheel speed sensor 10 and a adoptive filter 24x to remove unnecessary frequency components in the input signal Vw according to the extracted angular frequency information ω. By this device, noise components are removed according to wheel speed while desired components are not removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wheel speed detecting device.

[0002]

2. Description of the Related Art Conventionally, a wheel speed sensor such as a pickup coil is disposed near a wheel to detect an electromotive force or an angular frequency corresponding to the number of rotations of a wheel, and convert this signal into a square wave to convert the signal into a square wave. A wheel speed detection device that detects a wheel speed based on an edge interval or the like is known.

[0003]

However, when the vehicle travels on a rough road or the like, the output of the sensor itself has a noise component due to the impact from the road surface, and noise electromagnetic waves are generated outside or inside the vehicle. In some cases, a noise component is superimposed on a signal transmission path from the sensor. Such a noise component deteriorates the detection accuracy of the wheel speed.

Therefore, it is conceivable to remove a high-frequency noise component having a frequency equal to or higher than a predetermined frequency using a low-pass filter, for example. However, since the output signal frequency of the sensor itself changes, if this exceeds the predetermined frequency,
Not only noise components but also signal components are removed.

The present invention has been made in view of the above problems, and has as its object to provide a wheel speed detecting device capable of detecting wheel speed with high accuracy.

[0006]

In order to solve the above-mentioned problems, a wheel speed detecting device according to the present invention receives a signal containing angular frequency information of an AC signal from a wheel speed sensor, and outputs the angular frequency of the input signal. In a wheel speed detection device that outputs wheel speed information according to information, an angular frequency extraction unit that extracts angular frequency information from an input signal, and at least unnecessary frequency components in the input signal according to the extracted angular frequency information. And a filter means for removing a part thereof.

According to this device, the filter means removes at least a part, and preferably all, of the unnecessary frequency components from the sensor, but the filter means removes the unnecessary frequency components in accordance with the angular frequency information extracted by the angular frequency extracting means. Since the components are removed, the desired components can be taken out even during such removal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wheel speed detecting device according to an embodiment will be described. The same reference numerals are used for the same elements or elements having the same functions, and overlapping descriptions are omitted.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a wheel speed detecting device according to an embodiment.

This vehicle has four wheels (front wheels W _FL , W _FR , rear wheels W _RL , W W) provided rotatably with respect to a vehicle body BDY.
_RR ). Wheel speed sensors 10, 10x, 10y, and 10W correspond to the wheels W _FL , W _FR , W _RL , and W _RR , respectively.
z are provided, and the output is proportional to the left and right wheel speeds. Here, the wheel speed sensors 10, 10x,
10y and 10z detect the rotation speed of the wheel electrically / magnetically or optically and output a pulse corresponding to the rotation speed. The number of pulses per unit time is proportional to the rotation speed, that is, the repetition angular frequency of the output AC pulse signal is proportional to the rotation speed of the wheel. In this example, the wheel speed sensor is a power generation type wheel speed sensor (magnetic pickup sensor: MPU) using a permanent magnet and a detection coil.

Outputs from the sensors 10, 10x, 10y, and 10z are input to an ECU (Electronic Control Unit) 100 disposed inside the vehicle, and the ECU 100 calculates the wheel speed of each wheel based on the input information. Then, the vehicle speed calculated from the calculated wheel speeds is displayed on a display device, and, if necessary, a driving means (for example, a brake, a suspension, etc.) for controlling the vehicle body behavior based on the wheel speeds is controlled. I do. For example, the ECU 100 controls the lock timing of the wheels W _FL , W _FR , W _RL , and W _{RR in} an ABS (anti-lock brake system) based on each wheel speed.

The method for calculating the wheel speed is as follows.
Since the same applies to signals from 0, 10x, 10y, and 10z, in this example, for simplicity, a configuration for obtaining wheel speeds (wheel speed information) from output signals of the sensors 10 on behalf of four sensors will be described. .

An AC signal output from the wheel speed sensor 10 is input to a processor 24 via an A / D converter 12. That is, the A / D converter 12 samples the AC signal from the wheel speed sensor 10 at a predetermined sampling timing, converts it into a digital signal, and supplies it to the processor 24.

The processor 24 processes digital signals using a program stored in the ROM 16, detects and outputs wheel speed information. The processor 24 and the ROM
16. The RAM 18 can be constituted by a microcomputer. Here, the sensor will be described briefly.

FIG. 2 is an explanatory diagram showing the relationship between the sensor R and the rotor R provided coaxially with the wheel _WFL .
A tooth surface is formed around the rotor R, and the shortest distance between the rotor R and the sensor 10 fluctuates in a pulsed manner according to the rotation. The sensor 10 outputs a signal Vw according to the distance change. By extracting the angular frequency ω from the AC signal Vw and dividing the angular frequency ω by the number N of teeth of the rotor, the rotational speed of the wheel is calculated.

FIG. 3 is a block diagram showing the internal configuration of the processor 24. The angular frequency ω of the AC signal input from the wheel speed sensor 10 via the A / D converter 12
Although the signal Vw including the information is in a digital state,
It shall be represented by the following equation.

[0017]

(Equation 1)

This angular frequency ω is proportional to the rotation speed of the wheel,
If the angular frequency ω is high, the wheel speed is high, and if the angular frequency ω is low, the wheel speed is low. The function f (ω) is the amplitude of the output signal of the wheel speed sensor 10 and depends on the angular frequency ω (wheel speed). Here, θ indicates the phase. As the wheel speed sensor 10, a semiconductor sensor using the Hall effect can be used instead of the MPU. In this case, f (ω) can be considered as a constant independent of ω.

The processor 24 includes an adaptive filter 24x for removing unnecessary angular frequency components from the AC signal Vw according to the angular frequency, and an AC signal Vw from which unnecessary angular frequency components have been removed.
An angular frequency extraction unit 24y that extracts an angular frequency ω from the motor and a divider 24z that calculates the wheel speed by dividing the extracted ω by the number of teeth of the rotor R. Angular frequency extractor 24y
The angular frequency ω extracted by the above is fed back to the adaptive filter 24x. The adaptive filter 24x functions as follows according to the input angular frequency ω.

FIG. 4 is a graph showing the relationship between the angular frequency ω and the gain of the input signal Vw, and FIG. 5 is a graph showing the relationship between the angular frequency ω and the cutoff frequency of the adaptive filter 24x.

Assuming that the original angular frequency ω corresponding to the wheel speed in the input signal Vw is ω ₀ , this component has the largest gain, and this is the central angular frequency, and the noise component is Distribute. Adaptive filter 24x is a band-pass filter, the high pass cut-off frequency omega _H is set to the high frequency side than the angular frequency omega _0, low cutoff frequency omega _L in the low-frequency side than the angular frequency omega ₀ Is set.

As the wheel speed increases, the angular frequency ω ₀ increases, but the cutoff frequency increases while following the increase in the angular frequency ω ₀ while maintaining the above relationship. Therefore, the noise component consisting of the unnecessary angular frequency component is removed from the signal Vw after passing through the adaptive filter 24x, but the signal component remains.

There are various methods for setting the high-frequency cutoff frequency ω _H , which is set, for example, to about 10 times the angular frequency ω ₀ . Similarly, the low band cut-off frequency omega _L may be set to about 1/10 of the example angular frequency omega _0. The adaptive filter 24x is preferably a band-pass filter, but even if it is a low-pass filter, a certain noise reduction effect can be achieved. Here, the adaptive filter 24x will be further described.

FIG. 6 is a block diagram showing the configuration of the adaptive filter 24x. The adaptive filter 24x is those which include at least the low-pass filter 24 _X1, which causes a phase delay in the output signal. Thus, in this adaptive filter 24x, contact the vertical phase compensation section 24 _X2 consisting of the phase shifting circuit or the like thereto, and is advanced the phase shift, is configured so as to compensate the phase of the resulting output signal. Finally, the angular frequency extraction unit 24y will be described.

FIG. 7 is a block diagram of the angular frequency extracting unit 24y. The angular frequency extraction unit 24y includes an arithmetic unit 14A that performs an operation for removing the phase component θ of the AC signal Vw from the AC signal Vw, and a converter 30 that extracts the angular frequency information ω based on the operation value. I have.

In this example, the output of the arithmetic unit 14A is ω ² · f ²
(Ω), and the converter 30 calculates the previously measured ω ² · f
A map storing the relationship between ² (ω) and ω is provided, and ω corresponding to ω ² · f ² (ω) input from the arithmetic unit 14A is provided.
Is output.

Input AC signal Vw = f (ω) · cos (ω
Although various configurations of the arithmetic unit 14A for outputting the output signal ω ² · f ² (ω) in response to (t + θ) are conceivable, a preferred configuration is shown in FIG. That is, the arithmetic unit 14A includes a differentiator 14a, multipliers 14b and 14d, an integrator 14c, a subtractor 14e, and differentiators 14x, 14y, and 14z.

More specifically, the arithmetic unit 14A receives the input signal V
It has a differentiator 14y for differentiating w (cos wave) with time, and a multiplier 14b for squaring the differential value of the differentiator 14y. Thereby, the square function (= Vb) of the sine wave is output from the multiplier 14b.

The arithmetic unit 14A includes an integrator 14c for sequentially integrating and differentiating the input signal Vw with time and a differentiator 1
4z, which is used as signal transmission means. Here, since the signal transmission means functions as a signal transmission path that does not perform signal processing as a result, the integrator 14c and the differentiator 14z can be omitted. In other words, the output value of the signal transmission means is It suffices if the result is integrated and differentiated.

Further, the arithmetic unit 14A is provided with a group of differentiators 14a and 14x for differentiating the input signal Vw once more than the number of times of differentiation by the differentiator 14y, and a multiplication for multiplying the output values of the signal transmission means and the second differentiation means. Vessel 14d. As a result, the square function of the cos wave (= V
d) is output.

The subtractor 14e adds the square functions Vb and Vd of the sine wave and the cosine wave by inverting one of the signs, and adds
Only the amplitude component is output. That is, in the case of the present example, the sign of the square of the sine wave and the sign of the square of the cosine wave are opposite, so that the square of the sine wave and the square of the cosine wave are input to the subtractor 14e as an adding means. , And the two codes are made to coincide with each other and added.

With this configuration, the amplitude component in the input signal is extracted, and the output from the subtractor 14e is ω ² · f ² (ω). In other words, the subtractor 14e
The output values of the first and second multipliers 14b and 14d are added so that an amplitude component can be extracted.

Differentiator 14y, multiplier 14b, differentiator 14
a, outputs Vy, Vb, Va, V of the differentiator 14x, the integrator 14c, the differentiator 14z, the multiplier 14d, and the subtractor 14e
x, Vc, Vz, Vd, and Ve are as follows. C
(Θ) indicates an integration constant depending on θ. In the following description, the n-th derivative of the function X is represented as X ⁽ⁿ⁾ .

[0034]

(Equation 2)

When the phase θ component can be ignored, the differentiators 14x, 14y and 14z may be removed from each path. In this case, the apparatus assumes that the AC signal Vw from the sensor 10 is a sine wave function having no phase shift, and branches the signal into three to form first, second, and third AC signals. Differentiating one AC signal and squaring it, integrating the second AC signal,
The frequency information in the input signal is extracted by differentiating the third AC signal, adding a value obtained by multiplying the integral value and the differential value, and the square value. The angular frequency extracting unit 24y can be variously modified.

FIG. 8 is a block diagram showing the internal configuration of the processor 24 when the wheel speed sensor 10 is a semiconductor sensor. The processor 24 includes a differentiator 31 at a stage preceding the arithmetic unit 14A, and the output of the arithmetic unit 14A is ω ^4.
f ² (ω). In this case, if the 7, conversion unit 30 has a map storing a previously measured ω ⁴ · f ² (ω) and the relationship of omega, ⁴ · omega input from the arithmetic unit 14A It is assumed that ω corresponding to f ² (ω) is obtained and output.

In the above description, the output ω ^{2 of the} arithmetic unit 14A
· Corresponding ω based on f ² (ω) or ω ⁴ · f ² (ω)
Is read from the map, but the lookup table method is used.
The angular frequency information ω as the wheel speed information may be extracted by deleting the function f (ω) using 4B.

FIG. 9 is a block diagram showing the internal configuration of the angular frequency extracting unit 24y in such a case. in this case,
Input signal Vw is branched into two in the circuit, One of the branched signals is input to the arithmetic unit 14A sequentially through a differentiator group _{24 a1, 24 a2 ··· 24 an} , the other signal differentiator is input to the arithmetic unit 14B sequentially through a group _{24 b1, 24 b2 ··· 24 bn} , 24 bn + 1. In other words, the input signal Vw =
f (ω) · cos (ωt + θ) is time-differentiated n times while passing through one path and n + 1 times while passing through the other path.

By one differentiation, the cos function or si
The angular frequency ω in a trigonometric function such as an n function is included in the amplitude component. In other words, the order of the angular frequency ω increases in proportion to the number of times of differentiation. That is,
The order obtained by differentiating Vw n times and that obtained by n + 1 times differ from each other, and the function values represented by ω and f (ω) with the phase component removed from the arithmetic units 14A and 14B. Is output.

Since the order of f (ω) of these function values is the same and the order of ω is different, it is necessary to input these to the divider 24c to eliminate f (ω). Thus, a function of only the power of the wheel speed information (angular frequency) ω can be obtained. When the divider 24c outputs the k-th power of ω, the k-th root calculator 24d arranged on the subsequent stage side
Calculates the k-th root of this. Therefore, ω is output as a result from the angular frequency extraction unit 24y.

Note that f (ω) often differs from vehicle to vehicle due to sensor assembly errors and the like.
Since c eliminates the function f (ω), there is an advantage that such an effect can be suppressed.

As described above, the wheel speed detecting device receives the signal including the angular frequency information ω of the AC signal Vw from the wheel speed sensor 10 and outputs the wheel according to the angular frequency information ω of the input signal. In a wheel speed detection device that outputs speed information (ω or ω / N), an angular frequency extracting unit 24y that extracts angular frequency information ω from an input signal Vw, and an input signal Vw according to the extracted angular frequency information ω Filter means 24x for removing at least a part of unnecessary frequency components therein
And

According to the present apparatus, the filter 24x removes at least a part, and preferably all, of the unnecessary frequency components from the sensor 10, but the filter 24x uses the angular frequency information ω extracted by the angular frequency extractor 24y. , The unnecessary frequency component is removed in accordance with the condition (1), so that the desired component can be taken out even during such removal.

The ECU 100 including the above-described ECUs determines the wheel WFL, ABS at the ABS based on the determined wheel speeds.
Since the lock timing of WFR, WRL, and WRR is controlled, more accurate ABS control can be performed.

[0045]

As described above, according to the wheel speed detecting device according to the present invention, the wheel speed can be detected with high accuracy by reducing the noise component.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a wheel speed detection device according to an embodiment.

FIG. 2 shows a rotor R provided coaxially with a wheel WFL.
FIG. 4 is an explanatory diagram showing a relationship between the sensor and the sensor 10.

FIG. 3 is a block diagram showing an internal configuration of a processor 24.

FIG. 4 is a graph showing a relationship between an angular frequency ω and a gain of an input signal Vw.

FIG. 5 is a graph showing a relationship between an angular frequency ω and a cutoff frequency by an adaptive filter 24x.

FIG. 6 is a block diagram showing a configuration of an adaptive filter 24x.

FIG. 7 is a block diagram showing an internal configuration of an angular frequency extraction unit 24y.

FIG. 8 is a block diagram showing an internal configuration of an angular frequency extracting unit 24y according to another embodiment.

FIG. 9 is a block diagram showing an internal configuration of an angular frequency extraction unit 24y according to still another embodiment.

[Explanation of symbols]

10. Wheel speed sensor, filter means 24x, angular frequency extraction means 24y.

Claims (1)

[Claims] 1. A wheel speed detection device which receives a signal including angular frequency information of an AC signal from a wheel speed sensor and outputs wheel speed information in accordance with the angular frequency information of the input signal. Wheel speed detection, comprising: angular frequency extracting means for extracting angular frequency information; and filter means for removing at least a part of unnecessary frequency components in the input signal according to the extracted angular frequency information. apparatus.