JP3290492B2 - Signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device, and more particularly to a signal processing device capable of improving an S / N ratio.

[0002]

2. Description of the Related Art In general, noise such as an ignition signal is superimposed on an output of a sensor attached to a signal generating source, for example, a knocking sensor for detecting knocking of an internal combustion engine mounted on an automobile, in addition to a signal. In general, a filter mainly including a coil and a capacitor is used to remove a noise component.

[0003]

However, if the selectivity Q is increased in order to improve the S / N ratio, ringing may occur, and the S / N ratio may worsen.
In order to solve this problem, a processing device using a wide-band resonance type sensor has been proposed, but the signal itself is attenuated.

[0004] Further, there has been proposed a processing device for interrupting the input of the output from the sensor for a certain period at the timing when the signal generating source generates noise. However, during the interruption, the signal itself has been discarded. The present invention has been made in view of such a problem, and has as its object to provide a signal processing device capable of improving the S / N ratio without attenuating or discarding a signal.

[0005]

Means for Solving the Problems A signal processing apparatus according to the first invention, the unit time is an integral multiple of the reciprocal of the self-resonant frequency of the sensor signals detected by Rousset capacitors to detect a signal of a specific frequency A first-stage signal processing element including a delay element for delaying, and an addition element for adding an output of the delay element and a signal detected by the sensor;
N stages of N or more natural numbers that are cascade-connected and configured by a delay element that delays the output of the delay element by a unit time, and an adder that adds the output of the delay element and the output of the previous adder A signal processing device comprising: a signal processing element; and an output of the N-th stage addition element.

In the signal processing device according to the second invention, the delay time of the delay element is set to an integral multiple of the periodic operation state quantity of the signal generation source to which the sensor is attached. A signal processing device according to a third invention uses a subtraction element for subtracting the output of the delay element from the output of the sensor in place of the addition element in the first-stage signal processing element.

A signal processing device according to a fourth aspect of the present invention changes the number of stages of the cascaded signal processing devices in accordance with the operating state of the signal generation source.

[0008]

In the signal processing device according to the first invention,
The signal is multiplied by (N 2) by adding the signal that has been converted to a periodic signal by delaying the sensor output by a unit delay time that is an integral multiple of the reciprocal of the sensor's self-resonant frequency and the signal that is not subjected to delay processing. Noise is N
Since the signal processing elements are only multiplied, the S / N ratio is improved by (10 × log N) dB by cascade connection of the signal processing elements.

In the signal processing device according to the second invention, the delay processing is performed in accordance with the noise generation timing of the signal generation source. In the signal processing device according to the third invention, it is possible to improve the responsiveness by reducing the delay time to half. In the signal processing device according to the fourth invention, the number of stages of the signal processing elements is changed according to the operation state of the signal generation source, and the signal delay is reduced when noise is small.

[0010]

FIG. 1 is a block diagram of an embodiment of a signal processing device according to the present invention, which is used as a signal processing device of a knocking sensor attached to an internal combustion engine of an automobile, and the processing device itself is a microcomputer system. Be composed. That is, the knocking sensor 11 is directly attached to the internal combustion engine, and detects the vibration of the cylinder block of the internal combustion engine when knocking occurs.

The output of the knocking sensor 11 is input to a signal processing unit 12 configured as a microcomputer system. The signal processing unit 12 includes a CPU 122, a memory 123, and an A / D converter 124 with a bus 121 as a center. The signal from knocking sensor 11 is converted into digital information by A / D converter 124, and is converted into digital information according to a program stored in memory 123.
Processed in U122. Then, a known ignition angle control for suppressing knocking is executed based on the knocking signal after the processing.

FIG. 2 is a functional diagram of the first embodiment,
The output of knocking sensor 11 is delayed by delay element 2i (1 ≦ i ≦ N) connected in N stages. In the delay element 2i, the resonance frequency f _{0 of the} knocking sensor 11
The input signal is delayed by a unit time T which is an integral multiple (m / f ₀ ) of the reciprocal of Hz. That is, T = m / f ₀ holds.

In the addition element 3i (1 ≦ i ≦ N),
The output of the delay element 2i is added to the previous addition element 3 (i-1). Here, the output signal of knocking sensor 11 is x
When _s (t), the power Px _s signal is represented by the formula (1).

[0014]

(Equation 1)

Output signal x _{s of} knocking sensor 11
A signal obtained by adding (t) i times for each cycle T, that is, an adding element 3i
The output y _si (t) is expressed by equation (2).

[0016]

(Equation 2)

Here, the output signal x of the knocking sensor 11
_{Since s} (t) is a periodic function of the period T, Expression (3) holds.

[0018]

(Equation 3)

Therefore, equation (2) can be transformed into equation (4).

[0020]

(Equation 4)

Therefore, the power P _ysi of the output y _si (t) of the adding element 3i can be expressed by the following equation (5).

[0022]

(Equation 5)

On the other hand, if the noise is x _n (t), the power P _xn of the noise can be expressed by equation (6).

[0024]

(Equation 6)

The mutual power R _xn of the noise itself is given by the following equation (7).
, And if the noise is white noise, its value is “0”.

[0026]

(Equation 7)

Furthermore the y _ni output of i times adding the signal or summing element 3i noise x _n (t) to each period T of the formula (8)
It is represented by

[0028]

(Equation 8)

Therefore, the power P _yni of the output y _ni (t) of the adder 3i can be expressed by the following equation (9).

[0030]

(Equation 9)

In other words, according to the configuration of FIG. 2, as is apparent from equations (5) and (9), the power of the signal is multiplied by the square of the number of delay stages, while the power of noise is only multiplied by the number of delay stages. Instead, the so-called S / N ratio is improved by the number of delay stages. Here, the delay time T of the delay element i is set to an integral multiple of the ignition cycle or the rotation cycle of the internal combustion engine, and the processed signal y _si (t) is subtracted from the output signal x _s (t) of the knocking sensor 11. In addition, it is possible to reliably remove the noise at the time of ignition, which is the largest noise.

FIG. 3 is a functional diagram of the second embodiment.
This is a signal processing device in which delay elements are cascaded in three stages. FIG.
The difference from this is that the delay time of the delay element 2i is set to T / 2, and the subtraction element 311 is used instead of the addition element 31.
The point is to use. According to this configuration, the subtraction element 311
Can be obtained as the output of the adder 31 shown in FIG. 2 and the delay time can be halved, so that the amount of rounding of the waveform by the time delay element can be reduced.

FIG. 4 is a frequency characteristic diagram of the second embodiment, where the horizontal axis represents frequency and the vertical axis represents gain. That is, if the delay elements 2i are cascaded in 2 k steps (here, 2 steps), the frequency is at least 2 (n-1) f ₀ (n = 1, 2, 3,...), That is, the resonance frequency f of the knocking sensor. _{Since the} gain becomes zero at an even multiple of ₀ , it is possible to reliably block even-order harmonics and frequency noise components contained in the knocking sensor output.

Here, a is a two-stage delay element (k = 1), b
Represents four delay elements (k = 2), and c represents eight delay elements (k
= 3) is a frequency characteristic diagram in the case of (3). In addition, when the frequency characteristic diagram is represented by an equation in more detail using k, 2 (n−1) f ₀ ± f ₀ · L / 2 ^k−1 (k = 1, 2, 3,..., L is 2 ^k Natural number up to ^-1 ).

Further, a changeover switch 41 is additionally provided to output the output of the signal processing device according to the operating state of the internal combustion engine to the subtraction element 311, the first and second addition elements 32 and 33.
When the noise is high, the number of delay elements to be used is increased to increase the S / N ratio when there is a lot of noise. It is also possible to reduce the influence of the time delay due to this. In this embodiment, the application of the knocking sensor to the signal processing device has been described. However, it is apparent that the present invention can be applied to a signal processing device of another type of sensor used in an environment where periodic noise is superimposed. It is.

[0036]

According to the signal processing apparatus of the first invention, the power ratio between the sensor output as a periodic signal and the noise as a random signal, that is, the S / N ratio is improved according to the number of time delay stages. Becomes possible. According to the signal processing device of the second invention, the delay time of the time delay element is determined according to the operation state amount of the signal generation source, so that noise generated in synchronization with the operation state is reliably removed. Becomes possible.

According to the signal processing device of the third aspect, not only the delay time of the delay element can be halved and the amount of signal rounding can be reduced, but also the even-order harmonics can be reduced. It is also possible to reduce noise. According to the signal processing device of the fourth aspect, by switching the number of delay elements to be used according to the operation state, it is possible to improve the S / N ratio and reduce the amount of time delay.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a functional diagram of the first embodiment.

FIG. 3 is a functional diagram of a second embodiment.

FIG. 4 is a frequency characteristic diagram of the second embodiment.

[Explanation of symbols]

 11 Sensor 12 Microcomputer 2i (1 ≦ i ≦ N) Delay Element 3i (1 ≦ i ≦ N) Addition Element 311 Subtraction Element 41 Switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 17/06 653 H03H 17/02 601 F02D 45/00 368

Claims (4)

(57) [Claims] Wherein the delay element 1. A to the unit time delay is an integer multiple of the signal detected by Rousset capacitors to detect a signal of a specific frequency inverse of the self-resonant frequency of the sensor, the output of the delay element sensor A first-stage signal processing element composed of an addition element for adding the signal detected by the first stage, a delay element for delaying the output of the delay element of the preceding stage by the unit time, and an output of the delay element and the output of the preceding stage. A signal processing device comprising: an adder element for adding an output of the adder element; and N-stage signal processing elements which are two or more natural numbers and are connected in cascade, A signal processing device that uses the output of an element as its output. 2. The signal processing device according to claim 1, wherein a delay time of the delay element is an integral multiple of a periodic operation state quantity of a signal generation source to which the sensor is attached. 3. The signal processing device according to claim 1, wherein a subtraction element for subtracting an output of a delay element from an output of the sensor is used instead of the addition element in the first-stage signal processing element. 4. The signal processing apparatus according to claim 1, wherein the number of stages of the signal processing apparatus connected in cascade is changed according to an operation state of the signal generation source.